462 CETACEA. 



artery along the neck somewhat superficially, and then continuing for another inch 

 it terminates in a rete mirahile as on the left side, immediately external and anterior 

 to the junction of the first sternal rib with the manubrium. There is no defined 

 axillary, and therefore no brachial artery, properly so called ; this latter vessel being 

 represented by a rete mirahile following the nerve as on the right side. The left 

 posterior thoracic artery arises about two inches and a quarter from the origin of 

 the left subclavian artery. 



The most remarkable feature of these vessels is the abrupt manner in which 

 the branches are given off in dense tufts to form a rete mirahile ; also the cu'cum- 

 stance that the main arteries, themselves proceeding from the arch of the aorta, 

 terminate abruptly in a similar rete mirahile. 



The preceding description has been taken from a newly dead dolphin, the 

 vessels of which were carefully injected immediately after death. The parts 

 about the neck of this Cetacean are usually difficult to demonstrate, as they 

 very rapidly decay. And even in specimens well preserved in alcohol, and to 

 all ajjpearance quite unimpaired, I have yet invariably found that decay had 

 set in at the neck, doubtless from the amount of blood with which this region 

 is surchai-ged. 



Jiraiii. — Those who have attempted to preserve and examine the cerebral 

 substance in mass in a hot climate will appreciate the difficulties of so doing. I sac- 

 ceeded in extracting the brain of one animal, but the fluid in which it was neces- 

 sary at once to preserve it so shrunk the organ as to destroy many of its prominent 

 features (PL XXX, figs. 1, 2, and 3). I afterwards had recourse to taking an 

 internal cast of the cranial cavity, wMch has supplied certain data defective in the 

 preserved brain. In the following wood-cut (Eig. 16, p. 467) I have given the 

 outlines of the casts of the brain cavities of Orcella and of Flatcmista, the former 

 enclosing the latter, both having been drawn to one scale so as to bring out the 

 differences in form and size of their brains, the two animals from which the casts 

 were taken having been of similar length. 



I shall first describe separately the brain itself with its convolutions, &c., and 

 then the plaster mould, and lastly draw attention to the distinctions between this 

 latter and that of Orcella. It is to be borne in mind that what I state with res'ard 

 to the dimensions, &c., of the preserved brain requu-es to be modified by what obtains 

 in the cast. 



The brain taken from the alcohol had an antero-posterior measurement of 2-90 

 inches, a transverse diameter of 2-65 inches across the occipito-temporal regions, 

 though only a width of 2-20 inches at the frontal regions, its greatest vertical height 

 or depth being 2-10 inches. The cerebellum was a couple of inches broad, an inch 

 and two-tenths long, and rather less than one inch deep. Not only had the preserva- 

 tion in spirit diminished its size as a whole, but the tendency was to give the 

 brain a more irregular lob-sided appearance than it originally possessed, or than 

 the mould warranted. Nevertheless, even in the fresh condition, there was an appre- 

 ciable difference between the two sides, and, as will be shown, the convolutions of 



