mogastric lobule, where it lies close to, but above the portio mollis. After traversing the internal meatus, it passes through the Fallopian aqueduct, in which it is joined by the lesser petrosal nerve from the otic ganglion, and the greater petrosal, or vidian, from Meckel's ganglion. Where the latter nerve strikes it, a swelling-the intumescentia ganglioformis-is found, from which the corda. tympani arises; and beyond this it supplies the stapedius and tensor tympani, and emerges through the stylomastoid foramen. In the parotid it sends off auricular stylohyoid, digastric, cervico-facial, and temporo-facial branches, the latter forming the pes anserina, which supplies all the superficial muscles of the face. Its distribution in man and other animals, and the effects of division or disease, clearly demonstrate its function to be purely motor. It is the nerve of facial expression, and varies in animals in size according to the amount of this power. It supplies the muscles of the soft palate by a branch sent back along the vidian nerve. Its branch, the corda tympani, supplies the lingualis muscle. Its function is beautifully indicated by that common affection termed Bell's palsy, in which this nerve is alone affected. When the cause is intracranial, the eye remains open, the tears overflow, the brow and face are unwrinkled and expressionless, the cheek puffs, and the air escapes through the corner of the mouth if the patient tries to whistle; the ala nasi is loose, deafness happens, and, in some way, taste is impaired so that four of the organs of special sense are affected. The patient's utterance is also often imperfect, from the injury to the lingualis and palatine branches. The sketch of the anatomical distribution of the nerve we have given above, explains all these symptoms.

The Accessory nerve is quite peculiar in origin, as it takes root, by 6 or 8 filaments between the anterior and posterior roots, along the side of the spinal cord, as low as the 5th cervical nerve. Passing up through the

foramen magnum, it again leaves the cranium by the jugular foramen, sends a large branch to the pneumogastric, pierces the sterno-mastoid, and supplies the trapezius. Experiments have afforded very clear proof that the branch it sends to the vagus is motor, and is mainly sent to the larynx, to which it goes directly in quadrumana. The sterno-mastoid and trapezius are also supplied by the cervical plexus. Sir C. Bell regarded the accessory as a respiratory nerve.

The Pneumogastric, which is the most extensively connected of all nerves, arises in the groove between the olivary and restiform bodies, and escapes by the jugular foramen. Below this it forms a swelling often termed the laryngeal ganglion of Sir A. Cooper, and in passing over the subclavian artery swells into the plexus ganglioformis of Vieussens. Its course in the neck, thorax, and abdomen forms an important anatomical study, and is depicted on page 291. Its main branches are: 1. Communicating; 2. Pharyngeal, motor to the muscles of pharynx; 3. Superior laryngeal, sensitive to mucous surface, and a twig to the crico-thyroid, which can be traced back to the accessory; 4. Cardiac, which join the cardiac plexus; 5. Inferior or recurrent laryngeal, so called from winding round the subclavian on right side, and the arch of the aorta on the left. Mr. Hart, late Professor of Anatomy in our College, has explained this course by the relations of the brain and larynx to the great vessels in early life. In birds it passes direct to the lower or vocal larynx. This nerve supplies all the laryngeal muscles, save the crico thyroid, and, according to Reid, sends sensitive filaments to the trachea. 6. Pulmonary branches, forming the anterior and posterior pulmonary plexuses. 7. Esophageal, which form the plexus gulæ. 8. Gastric branches, which can be traced into the submucous or nervous coat of the stomach.

Most numerous experiments have been performed on the pneumogastric nerve. Irritation produces vermi

cular motion of the stomach. When they are divided, loathing of food is at first observed, but the animals afterwards eat without the feeling of satiety; gastric juice is still poured out and digestion proceeds. Brodie stated that after section of these nerves no mucus was poured out, so that arsenic killed more rapidly and the coats of the organ were themselves digested-but such results cannot always be obtained. When divided in a rabbit above the œsophagus, the animal eats so voraciously that the food accumulates in the stomach, oesophagus, and air-passages. The cardiac filaments seem to have a common action with the sympathetic on the heart. Section of one nerve does not materially affect respiration; but if both are divided above the lungs the animal dies in about 3 days, unless the ends are kept close together, when they survive 12. The animal suffers from dyspnoea, the "besoin de respirer" still existing, and after death the lungs are found congested and engorged with a serous fluid, due partly to the inflammation which foreign bodies produce by entering the air passages. If the superior laryngeal nerve is divided, irritants produce no effect on the glottis, which before was exquisitely sensitive. Irritation of the inferior laryngeal produces spasm of all the muscles save cricothyroid; and division of it produces paralysis of them followed by death, as the arytenoid cartilages fall together the apnoea occurring more rapidly in young animals on account of the cartilages being more movable. Magendie regarded the superior as the constrictor, and the inferior as the dilator nerve of the organ; and thus accounted for death by the unopposed action of the former when disease or injury destroyed the latter. Partial or complete aphonia is another effect of injury to the recurrent nerve. Many diseases, such as spasm of the glottis, hooping-cough, stomach-cough, &c., are due to reflex action of this great trunk by irritation of some of its branches.

QUESTIONS FOR EXAMINATION.

JUNIOR.

1. Describe the structure and uses of the upper eyelid. Is there any rudiment of a third eyelid ?

2. Explain the action of the agents by which we produce dilatation and contraction of the pupil.

3. What is the form of the human eye? Describe the coats which preserve its form permanently.

4. What is the structure and use of the inner coat of the choroid?

5. Enumerate the dioptric media.

6. Describe the structure of the optic commissure and nerve. 7. Give a short sketch of the nature, components, and properties of light, and explain what is meant by complementary colours. 8. Sketch the physiological purpose of each part of the external

ear.

9. Enumerate the openings in the tympanum, and describe the structures which fill the largest of them.

10. Describe briefly the labyrinth and the structures which fill the semicircular canals.

11. What is the function of the facial nerve, and how has it been proven?

12. Mention the results which follow section of the pneumogastric opposite the following points: 4th cervical, 3rd and 8th dorsal vertebræ.

SENIOR.

1. Explain the movements of the eyeball, and the arrangements of the orbit to permit them.

2. Describe the tunica vaginalis oculi of O'Ferrall, and the practical deductions which follow from its study.

3. What are the symptoms of disease of the oculo-motor nerve? 4. Describe the layers of the cornea and the changes they undergo in staphyloma.

5. What means are there for regulating the amount of light admitted to the retina?

6. Sketch the structure of the various layers of the retina, particularising any appearances presented by it posteriorly.

7. What is Prof. Hayden's view of the function of the yellow spot?

8. Relate what happens to a ray of light as it passes through the eye.

9. What powers render the eye superior to any artificial combination of lenses, and what are its most common optical defects?

10. How are the vibrations carried from the membrana tympani to the fenestra ovalis, and how can the tensity of the chain be regulated?

11. Describe the spiral lamina, and say what functions have been assigned to each part of the internal ear.

12. State a few analogous parts in the eye and ear.

REPRODUCTION.

THE multiplication of individuals is accomplished in the vegetable and animal kingdoms in a great variety of ways, but in all cases the presence of a protoplast, or pair of protoplasts, is essential. The old doctrine of spontaneous generation was mainly supported by the production of infusoria and other minute organisms in places where no germ could be discovered, but the progress of microscopical science, as well as the following experiment of Schultze, has overthrown the hypothesis. This naturalist found that infusions of organic matter, if exposed to the influence of the air, warmth, and light, soon swarmed with living beings; but if he compelled the air to traverse sulphuric acid or solution of caustic potash, all germs were destroyed, and at the end of 3 months the infusions were free from all trace of animalcules. As we proceed we shall have further proof of the aphorism, omne vivum ex ovo," for which the immortal Harvey so perseveringly contended. He asserted that "all animals-whether they be swimming, walking, or flying animals, and whether they be born in the form of an animal or of an egge-are all generated after the same manner.' The numerous modes of reproduction are tabulated as follows by Prof. A. Thomson. I have added an example of each form:

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