disease or accident, transmitting the conditions to his child?"

Such cases have a unique position and I have purposely excluded them from consideration heretofore. In the literature are reported 7 cases of accident or disease in the parent with subsequent microphthalmus or anophthalmus in the offspring. When, however, we consider the enormous number of cases of loss of the eyes from such conditions, and the few cases of transmission, we may say that, from a medical standpoint, the danger of transmission from parent to child in these cases is very minimal. However, if heredity should appear, then it is subject to the same laws of heredity as though the cause were originally congenital.

II. BUPHTHALMUS.

Just as the eye may be too small to functionate properly, so also it may be too large. This state occurs in myopic or near-sighted people. But unless the condition is very serious, it can usually be remedied by the use of proper glasses. Therefore, although myopia is strongly hereditary, it would certainly not be practicable and hardly desirable to forbid the marriage of myopic people. But when the eye is pathologically enlarged, in the disease called variously buphthalmus, megalopthalmus and hydrophthalmus, there is also a possibility of heredity manifesting itself. Thus, Best reports a case of a mother and son with megalophthalmus. It is usually, however, present in the form of collateral inheritance. I have been able to collect the histories of only 7 families; 20 abnormal and 7 normal children, a percentage of collateral inheritance of 74%. The condition is very rare and no final judgment can be based on the few cases reported.

III. ALBINISM.

The interior of the normal eye is lined by a membrane which is absolutely black on account of the large amount of pigment which it contains. This with the pigmented iris in front serves to shut out the excess of light, just as the box of the camera prevents the rays of light from entering at the sides and spoiling the negative. But in the condition called albinism, most of this pigment is absent, and the light which enters the eye from all sides makes it impossible for the patient to see distinctly, though rarely, if ever, causing total blindness. This condition is also hereditary, but rarely by direct heredity. In animals, the direct inheritance of albinism is a well-known fact. I have been able to find only 5 cases of direct inheritance of albinism. The father was affected 2 and the mother 3 times; there were 17 children, of whom only 2 were affected, or 12%. So it would seem that there is little danger for the children in the marriage of an albino. Collateral inheri

tance, however, is very marked. In 8 families with 43 children there were 21 albinos, or 48%.

IV. FAMILY DEGENERATION OF THE CORNEA.

As long as the cornea, or clear part of the eye, is unaffected, rays of light can pass through it without hindrance. But if it is clouded by opaque spots, the image cast upon the retina is more or less distorted, as would be the case if the lens of a camera had a flaw in it. Sometimes the opacities are so dense that rays of light barely pass through and all the patient can see is the outline of large objects and the difference between day and night. Altogether I have collected the histories of 18 families, 10 fathers and 8 mothers, with 62 children, of whom 26 were diseased, or 42%. Thirteen families with 50 children have been reported, of whom 34, or 68%, showed collateral inheritance. One family showed indirect heredity in two children, or 100%.

V. ANIRIDIA, AND COLOBOMA IRIDIS. The next structure we meet in the eye is the iris. This is the part of the eye which gives to it its color of blue, brown, hazel, etc. It may be entirely or almost entirely wanting, in which case it is called aniridia or irideremia. If only a portion is absent, it is called coloboma iridis. This condition shows marked direct heredity. For example, Galezowski reports the case of a woman with complete irideremia of both eyes and cataract in one eye. She had twelve children, all of whom had the same conditions. One of her daughters also had 12 children, all of whom had irideremia. Another daughter had 2 sons with irideremia. Another daughter was still alive, but no details of the history of her children could be obtained. All of the other children are dead. In this family of 27 members all had irideremia. Altogether I have found 58 families with direct heredity, the father being affected 29 times and the mother 29 times. To these must be added the case reported by of a

mother and 3 children with aniridia, 1 child normal. This makes 59 families with 29 affected fathers and 30 affected mothers; 116 affected children and 40 normal; total, 156. The percentage of affected children was 74%. Indirect heredity, from grandparent to grandchild, was present in only 4 cases, in which there were 8 children affected and 4 reported normal, or 66.6%. Collateral inheritance was found only 9 times; there were 31 children, of whom 23 were affected, or 74.2%.

VI. ECTOPIA LENTIS.

In the condition called ectopia lentis, the crystalline lens does not lie in its normal position, but is displaced more or less upward, downwards or to the side. As a result, the rays of light entering the eye are unequally

case.

refracted and more or less disturbance of vision takes place. Examples of direct heredity are numerous. Bresgen reports the following Bresgen reports the following The great-grandmother had been nearsighted from childhood. One granddaughter had ectopia lentis and all of her 6 children had the same condition. Another daughter, unmarried, also had ectopia lentis. A son had normal eyes, but his son had ectopia lentis. In this family we have either indirect or collateral inheritance in the third generation and direct and indirect in the fourth generation. In all 42 cases of direct heredity have been reported, the taint coming from the father in 19 cases and the mother in 23. There were 151 children, of whom 107 were affected, the percentage being 70. To these must be added the family reported by Dr.

-, making

43 families, 19 fathers and 24 mothers, 155 children, of whom 109 were affected, equaling 70%. There were 3 cases of indirect inheritance from grandparent to grandchild, with 12 children of whom 6 were affected, equaling 50%. There were 15 cases of collateral inheritance, with 42 children, of whom 35, equaling 83%, were affected.

VII. CATARACT.

Even if the lens is in its proper position, it may be opaque, so that the disturbance in vision ranges from very slight to only ability to distinguish between day and night, depending on the amount and location of the opaque spots. This is one of the most frequent forms of hereditary blindness. The cataract may ap pear very late in life, or may be congenital. In some cases, each succeeding generation is affected at an earlier age, a condition called anticipation. Berry reported a family where the history was known for seven generations. First generation was normal. There were 2 members to the second generation, both of whom were normal. In the third generation there were 10 children, of whom 5 had cataract. In the fourth generation there were 9 children, all of a cataractous mother, of whom 4 had cataract and 5 were normal. In the fifth generation there were 6 children, all of a cataractous mother, of whom 4 had cataract. In the sixth generation there were 10 children, descended as follows: A cataractous mother had 1 normal and 4 cataractous children; a cataractous father had 2 normal children; a cataractous mother had 1 normal daughter, and a normal mother had a normal son. The seventh generation had 21 children, as follows: A normal father had 10 normal children; a cataractous mother had 2 normal children and 1 cataractous daughter; a cataractous father had 1 cataractous daughter by his first wife and 3 normal children by his second; another cataractous father had 1 cataractous daughter and 2 normal children; a

normal mother had 1 normal child. Cooper stated in 1852 that he had been informed by the Duke of Sussex that cataract had been brought into the royal family of England by the marriage of one of his ancestors with a princess of Saxe-Coburg-Gotha. She had cataract and many of her descendants had the same affection. Among them was the Duke of Cumberland, who commanded at Fontenoy; George III, George IV, the Duke of Glouces ter, the Duke of Sussex, Princess Sophie, and the King of Hanover.

Including the cases reported in the letters received, I have succeeded in collecting the histories of 304 cases of direct heredity of cataract. The father was affected 145 times, the mother 152 times, not stated 7 times. There were in all 1012 children, of whom 589 had cataract, and 423 had normal eyes; percentage of affected children, 58. In other words, in every family of 5 children, where either the father or mother has cataract, 3 of the children will at some time suffer with cataract. The percentage would probably be higher were it not that so many people with cataract die young, and so leave no descendants.

I have found only one case where both the father and the mother had cataract. There were 8 children, 4 of whom were normal, 2 had cataract, and 2 unknown. To these must be added the cases reported by Drs. and

In one of these families there were 2 and in the other there were 5 children with cataract, in all 3 families with 15 children, of whom 9 had cataract, making 60%slightly more than where only one parent is affected. The number of cases is too small, however, for a general rule.

I have found 13 cases of indirect inheritance from grandparent to grandchild, and 16 cases of indirect inheritance from uncle or aunt to nephew and niece. There were in these 29 families 107 children, of whom 62 were normal and 45 had cataract, equaling 42%.

In the literature, 66 cases have been reported of collateral inheritance; that is, cases of two or more children in the same family having cataract, while all other relatives have been free. There were 118 normal and 186 cataractous children. To these must be added the cases reported by Drs. and

and making 68 families, with 119 normal and 193 cataractous children, or 61.8% of the latter.

VIII. RETINITIS PIGMENTOSA. Practically the only disease of the retina showing hereditary tendencies is the condition called retinitis pigmentosa. The principal complaint of the patient is a diminution of vision especially pronounced on a dark day and towards nightfall. There may, however,

be almost total blindness on even bright days. While this condition also shows direct heredity, its usual appearance is in the form of collateral inheritance.

As the

It is very often found in children of parents who were related before their marriage, although they, as well as all of their ancestors, may be apparently perfectly normal. question of advisability of consanguinous marriages is foreign to the subject of this paper, except in so far as the related parents are themselves diseased, I have kept no special record of such relationship, although I found many such cases. Cumer reports a family whose history of night blindness he had been able to trace back for 200 years. It always descended from parent to child, but not all of the children were affected. During this period of time 125 persons were affected.

Altogether, there have appeared in the lit erature the reports of 119 families, the father being affected 59 times and the mother 60 times. There were 387 children, of whom 195 had retinitis pigmentosa. To these must be added the cases reported by Dr. making a grand total of 126 families, 61 fathers and 65 mothers, 405 children, of whom 205, or 50%, had directly inherited the condition from the parent. In addition to these cases, there were 2 families where both parents were blind, and of the 10 children exactly one-half had the same disease.

There were 25 cases of indirect transmission; total of children, 71; affected, 52, or 73%.

Including the cases reported in the letters, there were 133 cases of collateral inheritance; total of children 541, of whom 349 were affected, or 64%. So not only is the actual number of cases larger, but the percentage of involvements is larger in collateral than direct inheritance, being 64% as compared to 50%.

IX. ATROPHY OF THE OPTIC NERVE.

In atrophy of the optic nerve, we are dealing with a condition comparable to destruction of telegraph wires. The apparatus may be entirely sound, but there is no way of communicating between two cities. In the same way, although all the parts of the eye may be normal, if the nerve is destroyed, the patient cannot see. Although atrophy of the optic nerve is hereditary, it is usually in the form of indirect heredity from uncle to nephew. Females are rarely affected, but their male children are frequently so. Still the disease may be transmitted directly, as the case reported by Batten. In this family, 1 boy and 2 girls, their mother, a maternal uncle and a maternal aunt were affected.

I have been able to collect 46 cases of direct heredity, with 120 children, of whom 56

were affected, or 46%. There were 43 cases of indirect inheritance, with 155 children, of whom 93, or 60%, were affected. Compare this with the 46% of direct and the preponderance of hereditary influence of this disease through the indirect line is seen at once. There were 61 cases of collateral inheritance with a total of 231 children, of whom 163 were affected, or 70%. The larger number of cases of collateral inheritance is due to the fact that many of the indirect and direct started as involvement of two or more children of one family group. X. GLAUCOMA.

Glaucoma has for a long time been known to be hereditary. Its principal symptoms are in acute cases very severe pain, and in all cases a more or less rapid loss of sight, which is due to the effect of the disease upon the optic nerve. Not all forms of glaucoma are hereditary. The acute form sometimes is, but it is usually the slow, progressive variety which is transmitted to the children, and it is just this form that is the most difficult to treat. Howe gives the following family history: I, male, glaucoma at age of 40. had 6 children, of whom 4 were normal; 1 son became blind at the age of 28, and 1 daughter became blind at the age of 25. The son had 5 children, 3 of whom had glaucoma. The daughter had 4 children, 2 of whom had glaucoma. In this generation the disease began between 17 and 28 years of age. This family shows distinctly anticipation of the disease and a large percentage of direct heredity.

He

I have been able to find 44 families with direct hereditary glaucoma, the father being affected 23 and the mother 21 times; there were 131 children, of whom 72 were affected, or 55%.

There were 13 cases of collateral inheritance, 53 children, of whom 33, or 62%, had glaucoma. There was one case of indirect heredity, 10 children, 4 affected, equaling 40%.

XI. NYSTAGMUS.

By this is meant a more or less continual movement of the eyes, which do not remain stationary long enough for the person to per ceive an object clearly. This condition is also hereditary. Sinclair reports the case of 2 children, their aunt and her 3 children, all of whom had nystagmus. Wood reports the following case: The grandfather had nystagmus; 1 daughter had the same condition, 10 children were normal. In the next generation 4 children were normal and 1 daughter had nystagmus.

In all there were 8 fathers and 10 mothers affected; of their 56 children 26, or 46%, were affected. There were 9 cases of collateral inheritance. Of the 40 children, 29, or 70%,

By this we mean a more or less complete paralysis of one or more of the muscles of the eye or eyelid. It is usually directly hereditary. For instance, Dujardin reports a family where the maternal grandfather, the mother and 4 daughters had bilateral congenital ptosis. Gourgein reports a case where the grandmother, an aunt, the father and 5 sons had double ophthalmoplegia, 3 daughters were unaffected. Guende reports a case of 3 brothers with the same condition. In all I was able to find the records of 32 cases. The father was affected 24 times, and the mother 8 times. Of the 121 children, 77, or 63%, were affected. One family had both parents affected; of the 6 children, 3, equaling 50%, were affected.

and parent are to be regarded as another family, and so on. Wherever possible, normal children have been counted as affecting unfavorably the probability of inheritance, but whenever this normal child has himself nor mal children, such a family of normal parent and children have been excluded from the calculation, as otherwise we would be estimating the proportion of blind to normal people, whereas we are desirous only of knowing the proportion of blind to seeing children of a blind parent.

In estimating the proportion of indirect inheritance, 1 child in a family was considered sufficient to show the existence of a hereditary taint if the same disease was present in some ancestor. Every normal child of that normal parent of course reduces by so much the proportion of indirect inheritance.

In collateral inheritance, at least two chil dren must be affected before the condition can

In the five cases of collateral inheritance there were 17 children, of whom 13, or 76%, were affected. One family showed indirect heredity, the only child being affected, equaling 100%.

CONCLUSIONS.

In conclusion, it would be well to recapitu late the facts that have been accumulated and to state what measures should be taken to prevent hereditary blindness. First of all, it would be well to show in graphic form the probabilities of inheritance by the direct, the indirect and the collateral forms. This is done in the following table. It should be remembered that in estimating the number of families affected with each condition, I have regarded each blind parent and his or her children as a separate and distinct family. If the parent is himself the child of an affected parent, then he with his brothers and sisters

33

9 40 29

874.2 13:77.0 68 70.0 119 61.8 5.88.8

16 68.0 20 62.0 774.0

11 70.0

4.76.0

192 64.5

113 385 226 159 58.7 363 1446 961 485 63.4

be hereditary, otherwise it would simply be an isolated unfavorable variation of one member of a family. With two affected, although all the rest may be normal, the family undoubtedly shows a hereditary taint. No one can object to this, since the larger the number of unaffected children, the smaller must be the proportion of affected ones. Whenever nothing was said in regard to normal children, it was assumed that there were none, and whenever the statement was made that a few or several other members of a family were or were not affected, that family was disregarded as possessing no statistical value. Whenever a child died before reaching an age where the disease could manifest itself, it was regarded as non-existant. Bearing these facts in mind, the importance of the above table will be recognized at a glance.

While it is true that no one can forecast the future absolutely, a thorough knowledge

it

of the events of the past will give us an idea of the probable results of similar conditions in the future. From a statistic average of the ages at which people die, the insurance companies are in a position to say that at such and such an age, out of 1000 people only a certain percentage will die. Whether will be you or your neighbor, they cannot say. It is the aggregate and not the individual which serves for comparison. So in the table here shown, the percentages arrived at have been based upon the largest possible statistics. That they are not absolutely fixed, I do not deny. There are doubtless cases of blind parents with normal children which have never been reported, but my letters have furnished me with proof that there are likewise cases of blind parents with blind children which have never been recorded. Who shall say whether or not the former outnumber the latter? Let us suppose, however, that each of the percentages is too high by 20%. This will bring the lowest, that of corneal degeneration and nystagmus, down to 22%, and the highest, that of aniridia and coloboma iridis, down to 52%. Then, even allowing this wide margin of error, in the former case 1-5 of all children of a parent with corneal degeneration will have the same condition, and 1⁄2 of all the children of a parent with aniridia will be similarly affected.

From a consideration of the facts which I have brought before you, I think the following conclusions are justified:

I. All those whose life-work brings them into relationship with the blind should be made acquainted with, if they are not already aware of, the dangers which are connected with the marriage of a blind person, whether to one of normal sight or to another blind person.

II. The blind themselves should be warned of the dangers to their children in case of marriage, and should be strongly advised to remain single.

III. A distinction must be made between hereditary and non-hereditary forms of blindness. In the former the chance of the child inheriting the parent's disease is too great to allow any option. In the latter, social and economic considerations enter, with which the present paper cannot concern itself.

IV. In addition to mere precept, legal assistance should be invoked to prevent the blind from marrying. This, in my opinion, could be most practically carried out by the license clerk inquiring if either of the parties had any disease of the eye. In case of an affirmative answer, a certificate from a reputable oculist should be required stating that the disease is non-inheritable. If a negative answer is returned, both parties should be compelled to write their names, as most of the sufferers from hereditary eye affections have lost their

vision to such an extent as to make even this somewhat difficult. If the clerk suspects from any reason that one or both of the parties are affected he shall refuse the license until a proper certificate is produced. This is analogous to the right of a clerk to refuse a license to those whom he believes to be under age in spite of their positive declaration to the contrary. That there are objections to this method of solving the difficulty, I do not deny, but it seems to me to be the most practical.

V. This law is to apply only to those cases of blindness where heredity has been proven, namely, microphthalmus and anophthalmus, family corneal degeneration, aniridia, coloboma of the iris, ectopia lentis, cataract, retinitis pigmentosa, glaucoma, nystagmus, atrophy of the optic nerve, strabismus and ophthalmoplegia. With the exception of glaucoma and of senile and presenile cataract, these diseases usually manifest themselves at or before the marrying age. In the two exceptions noted, unless they are of anticipating character, the damage has been done before the disease appears in the parent. Consequently, the offsprings of such parents may be totally igno rant, at the time of their own marriage, of their own danger and that of their children. It would be better for no descendant of a cataractous ancestor to marry, but it will be found impossible to prevent those from marrying who do not show the taint at the time of marrying.

VI. It would be inadvisable to pass a law compelling every person to have an oculist's certificate before being allowed to marry, although such a law would be the ideal condition. In the first place, it would work a great deal of hardship in those localities where there is no competent oculist. In the second place, the percentage of all blind people, as compared to people with normal sight, is small, according to the Swiss census of 1895-6, as reported by Dr. Paley, being between 7 and 8% in every 10,000. The percentage of those who are blind from hereditary disease is between 5 and 10% of the total number of blind people, so that less than 1 in every 10,000 people in any country would be affected by the law which I suggest. It would be impossible to enforce such a law upon 9999 persons in order to compell its observance by one, and the discretionary power in the hands of the license clerk would serve for the present.

VII. Finally, there is the important duty of educating the general public in dangers arising from hereditary blindness. They should be told that even though they may be normal themselves, if two of their children are blind there is the danger that from at least 28% to 68% of them will be blind according to the form of blindness from which they suffer, and