532 ZMBR7OL0Q7. 



2. At the deep end of the hair-germ the vascular hair-papilla 

 is begun by a growth of connective tissue. 



3. The epithelial hair-germ is differentiated into : — 



(a) A yoimg hair, by the cornification of a part of the cells ; 



(6) An actively growing cell-layer situated between the shaft 

 of the hair and the papilla, — the bulb, — which fur- 

 nishes the material for the growth of the hair ; 



(c) The outer and the inner sheaths of the root. 



4. Around the epithelial part of the fundament of the hair 

 there is formed from the surrounding connective tissue the hair- 

 follicle. 



5. The nails in Man and the claws in other Mammals are de- 

 veloped from a dorsal fvindament — the nail-plate — and a ventral 

 fundament — the plantar horn. 



6. The plantar horn in Man is reduced to the nail-welt. 



7. The thin nail-plate which is formed at first is for a time 

 covered with a layer of cornified cells, the eponychium, which in 

 Man is shed in the fifth month. 



8. The mUk-gland is a complex of alveolar glands. 



9. At first there arises a thickening of the mucous layer of the 

 epidermis, which is converted into the glandular area that is after- 

 wards marked off from the surrounding parts by a wall and becomes 

 somewhat depresr:ed. 



10. From the bottom of the glandular area there grow forth in 

 great numbers the fundaments of alveolar glands. 



11. After birth the glandular area, embracing the excretory 

 ducts of the glands, is elevated above the surface of the skin, and 

 converted into the nipple and the areola mammae. 



12. After birth there is a transitory secretion of a small quantity 

 of milk-like fluid — the \vitches' milk. 



LITERATURE. 



(1) Develojiment of the Nervous System. 



Ahlborn. Ueber die Bedeutung der Zirbeldriise. Zeitsohr. f . wiss. Zoologie. 



Bd. XL. 1884. 

 Altmann, R. Bemerkungen zur Hensen'sohen Hypothese von der Nerveu- 



entstehung. Archiv f. Anat. u. Physiol. Physiol. Abth. 1885. 

 Balfour. On the Development of the Spinal Nerves in Elasmobranoh Pishes. 



Philos. Trans. Koy. Soc. London. Tol. CLXVI. 1876. 



