BAL^ENOPTERA ROSTRATA. 117 



not so much as in the human ; and in the whale-class it is still less, 

 but not so little as in the birds, &c. 



The brain is composed of cortical and medullary substances, which 

 are very distinct : the cortical is in colour like the tubular substance 

 of the sound kidney; the medullary is very white 1 . The cortical and 

 medullary bear near the same proportion [to each other] as in the human 

 [brain]. The two lateral ventricles are large 2 , and are not continued 

 into the olfactory nerves 3 . The medulla spinalis is small for the size of 

 the animal, having a cineritious substance in the centre 4 . 



Of the Tail. — The mode in which the tail is constructed is perhaps as 

 beautiful a part as any in the animal. It is wholly composed of three 

 layers of tendinous fibres, covered with the common cutis and cuticle. 

 Two of these layers are external, the other internal. The direction of 

 the fibres of the external layers is the same with the general surface of 

 the tail, and they make a stratum about a quarter of an inch in thick- 

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

 internal layer is composed entirely of tendinous fibres passing directly 

 across between the two external layers above described : the length of 

 the fibres accords with the thickness of the tail 5 . This structure gives 

 additional strength to the part. The structure of the tail is so firm and 

 compact that the vessels retain their dilated state. The canal through 

 the substance of the tail has passing [through it] a large middle vessel, 

 surrounded with as many smaller ones as can be placed on the external 

 surface of the larger ; which are arteries and which are veins I do not 

 know. The fins are only covered with a strong condensed adipose 

 membrane. 



Of the Eye. — A transverse section of the eye is a short ellipse, and the 

 cornea is rather a longer one than the globe. The two sides of this 

 ellipse are not equally curved, the superior being the most so. The 

 long axis is in the direction of the animal, and the cornea is veiy 

 flexible, soft and thick. The external shape of the sclerotic without 

 the cornea, on a lateral view, is a flattened sphere. The cornea is a 

 smaller circle placed upon it, as in most eyes. There are four straight 

 muscles that come pretty far forwards on the eye, and which are not 

 very strong ; behind these there is a circular muscle which is inserted 

 into the eye pretty near its greatest axis or middle, but rather behind it. 

 This, although almost circular, yet is divisible into three or four portions 

 at its insertion ; it is much stronger than the former muscles. The two 



1 [Hunt. Preps. Nos. 1335, 1336, "showing a fibrous structure."] 



2 [The ' plexus choroides ' is preserved in Prep. No. 1337.] 



3 [Hunt. Preps. Nos. 1545, 1546.] 4 [lb. Nos. 1363, 1364.] 

 5 [lb. Nos. 1844, 1845.] 



