388 



MANUAL OF HISTOLOGY. 



fine canals in the tadpole's tail have a similar origin to the blood capil- 

 laries. 



The pathological new formation of lympatic vessels has been remarked, 



Fig. 388. The same region after the lapse of twenty-four hours. 



however, as, for instance, in pseudo-membranes and adhesions, by Schroder 

 van der Kolk, E. Wagner, and Teichmann. W. Krause was the first to 

 demonstrate their presence in tumours by injection. 



18. The Hair. 

 212. 



The hairs are productions of the corneous embryonic plate. They are 

 filiform appendages, composed of a modified epithelial tissue, and are of 

 rather complex structure. In hairs we have to distinguish between the 

 shaft (fig. 389, Z), which projects beyond the skin in the greater parb of 

 its length, and terminates above in a point, the root or lower portion 

 which is concealed in the skin, and ends in a flask-shaped duplicature of 

 the latter, called the hair follicle (a), and the bulb, which is the thickened 

 and rounded terminal portion (/?). The latter, hollowed out below, is 

 seated on a papilla (i) rising from the floor of the follicle. Between the 

 follicle and the proper hair is found a complex encasing sheath, which is 

 divided into an external (c) and internal portion (d). 



It may be found most convenient if we commence our observations 

 with the most deeply seated portions of the structures in question, for in 

 them we have the source from whence the latter spring, and can observe 

 the earliest forms under which the tissue makes an appearance. In this 

 way we shall be best enabled to comprehend the further transformations 

 which take place until eventually the texture of the shaft is arrived at. 



The hair follicle (a) is a reduplication of the cutis vera of variable 

 length and oblique direction. In some cases, when the hairs are long, 



