THE ORDER CETACEA. 



41 



mon cutis and cuticle : two of these layers are external, 

 and the other internal. The direction of the fibres of 

 the external layers is the same as in the tail, forming a 

 stratum about one-third of an inch thick ; but varying, 

 in this respect, as the tail is thicker or thinner. The 

 middle layer is composed entirely of tendinous fibres, 

 passing directly across, between the two external ones 

 above described, their length being in proportion to the 

 thickness of the tail; a structure which gives amazing 

 strength to this part. 



The substance of the tail is so firm and compact, that 

 the vessels retain their dilated state even when cut 

 across ; and this section consists of a large vessel sur- 

 rounded by as many small ones as can come into con- 

 tact with its external surface : which of these are arteries 

 and which veins is not yet ascertained. 



Fig. 1. Fig. 2. 



A ^^ 



A TRANSVERSE SECTION OF 

 THE TAIL.* 



The above cuts are' representations of the posterior 

 part of the animal, being a section of one of the lumbar 

 vertebree and a portion of the tail. 



* Explanation of the Figures. — Fig. 1. 



A. — Skin with Epidermis. 

 B. — Cellular substance called blub- 

 ber. 

 C. — Cartilage enveloping the ten- 



dinous cells. 

 D. — Cells of strong muscular coat- 

 ing, through which the ten- 

 dons play. 



