LESSON 27.] 



HAIR. 



87 



If a thin transverse section be made of Baleen ( Whalebone), it 

 will be found to be composed of a dense aggregation of structures 

 resembling so many distinct hairs, each having its medullary canal, 

 surrounded by a cortical substance (Fig. 139). 



If now a longitudinal section be made, the medullary canals will 

 be very distinctly seen, divided periodically into a series of cellular 

 cavities by septa (partitions) transverse in their direction (Fig. 140). 



452. In structure, whalebone bears a wonderful resemblance to 

 hair (Fig. 139), agreeing most with the pachyderm type, which ad- 



FIG. 140. 



FIG. 139. 



Transverse section of Whalebone. Longitudinal section of Whalebone. 



mits a plurality of medullas. The cortical substance is divided into 

 a series of distinct bodies, each simulating a hair, and separate ; is 

 seen to be filled with medullary canals, which are, however, better 

 seen in the longitudinal section (Fig. 140). 



In the hair from the mane of a Horse, there is an exception to 

 the rule of development of pachydermatous animals, as only one 

 medullary canal appears (Fig. 141). 



453. The male Turkey (Meleagris galloparvo) is provided with 



FIG. 141. 



FIG. 142. 



Transverse section of hair, Horse's mane. Transverse section of hair from Turkey's beard. 



a tuft of very coarse hair, popularly known as the beard ; in trans- 

 verse section all the tissues are distinctly seen (Fig. 142). The 



