440 SUMMARY OF CURRENT RESEARCHES RELATING TO 



heteroplastic. But it is only the epithelial portion that can retain its 

 cellular vitality and individuality. The necrosed connective elements 

 are replaced by regenerating tissue. 



Hair of the Cat.* — Hermann Hofer has made a detailed study of 

 the hair of the cat. There are three kinds: (1) the main hairB 

 (Leithaare), marked by strength, length, and prominence ; (2) the 

 shorter wavy hairs (Grannenhaare), with alternate broader and narrower 

 regions ; and (3) the shortest, woolly hairs (Wollhaare), delicate and 

 undulating, with alternate broader and narrower portions, and with 

 little pigment. In a group there may be distinguished, according to 

 de Meijere, the primary hairs (Stammhaare), of which one may be 

 distinguished as the middle hair, and the subsequently developed acces- 

 sory or side-hairs. 



The medulla of the cat's hair is in a single row, like a necklace of 

 pearls or a rouleau of sovereigns ; the gas is intercellular. The shape 

 of the medullary cells in the thicker parts (main hairs and short hairs) 

 is somewhat different from that of the thin parts (woolly hairs and 

 proximal shaft of the short hairs). The cortex is relatively narrow and 

 without peculiarities. The cuticular cells can be well seen after treat- 

 ment with nitric acid ; they show great variability in shape and arrange- 

 ment in the different kinds of hairs in the cat ; but seem to be very 

 similar in the same kind of hairs in different animals. 



The hair-groups in the cat consist of an isolated median hair and 

 several lateral primary hairs, each of which has a number of accessory 

 hairs in a group or bundle. The median hair comes first, then a lateral 

 main hair on each side, so that at a certain stage, before and at 

 birth, the three-hair-group is prominent. The number of lateral primary 

 hairs increases gradually, and they are accompanied by their accessory 

 hairs. In the adult cat the groups become disguised. The sebaceous 

 glands are all at the same level. Each follicle-complex has its glandular 

 complex. Each median hair has a sudorific gland, and probably each of 

 the lateral primary hairs likewise. 



The hair-groups are disposed in longitudinal rows, and there is great 

 diversity in the size of the groups. The median hairs are long hairs, 

 the lateral primary hairs correspond to the short hairs, and the accessory 

 hairs to the woolly hairs. In development, which is described at length, 

 there is no difference in the earliest stage between the median hair and 

 the primary lateral hairs. In the papilla-stage and later there are 

 marked differences. The papilla-stage and later stages of the accessory 

 hairs show a close resemblance to the similar stages in the development 

 of the lateral primary hairs. 



Phylogeny of Mammalian Hairs.f — E. Botezat discusses the various 

 theories of the morphological nature of mammalian hairs. They have 

 been denied structural unity and regarded as parts of the epidermis, or 

 they have been interpreted as derivable from placoid scales, teeth, pearl- 

 organs of Cyprinoids, scales, parts of scales, integumentary sense-organs 



* Arch. Mikr. Anat., lxxxv. (1914) pp. 220-78 (2 pis.). 

 t Anat. Anzeig., xlvii. (1914) pp. 1-44 (2 figp.). 



