332 PHILOSOPHICAL TRANSACTIONS. [aNNO 1787. 



very muscular, they are very elastic, for being stretched they contract again very 

 considerably. There is nothing uncommon or particular in the structure of the 

 ventricles, in the valves of the ventricles, or in that of the arteries. The general 

 structure of the arteries resembles that of other animals; and where parts are 

 nearly similar, the distribution is likewise similar. The ^orta forms its usual 

 curve, and sends off the carotid and subclavian arteries. 



Animals of this tribe, as has been observed, have a greater proportion of 

 blood than any other known, and there are many arteries apparently intended as 

 reservoirs, where a larger quantity of arterial blood seemed to be required in a 

 part, and vascularity could not be the only object. Thus we find, that the 

 intercostal arteries divide into a vast number of branches, which run in a serpen- 

 tine course between the pleura, ribs, and their, muscles, making a thick sub- 

 stance somewhat similar to that formed by the spermatic artery in the bull. 

 Those vessels, every where lining the sides of the thorax, pass in between 

 the ribs near their articulation, and also behind the ligamentous attachment of 

 the ribsj and anastomose with each other. The medulla spinalis is surrounded 

 with a net-work of arteries in the same manner more especially where it comes out 

 from the brain, where a thick substance is formed by their ramifications and convo- 

 lutions; and these vessels most probably anastomose with those of the thorax. 



The subclavian artery in the piked whale, before it passes over the first rib, 

 sends down into the chest arteries which assist in forming the plexus on the 

 inside of the ribs; I am not certain but the internal mammary arteries contribute 

 to form the anterior part of this plexus. The motion of the blood in such must 

 be very slow; the use of which we do not readily see. The descending aorta 

 sends off the intercostals, which are very large, and give branches to this plexus; 

 and when it has reached the abdomen, it sends off, as in the quadruped, the 

 different branches to the viscera, and the lumbar arteries, which are likewise 

 very large for the supply of that vast mass of muscles which moves the tail. 



In our examination of particular parts, the size of which is generally regulated 

 by that of the whole animal, if we have only been accustomed to see them in 

 those which are small or middle-sized, we behold them with astonishment in 

 animals so far exceeding the common bulk as the whale. Thus the heart and 

 aorta of the spermaceti whale appeared prodigious, being too large to be con- 

 tained in a wide tub, the aorta measuring a foot in diameter. When we con- 

 sider these as applied to the circulation, and figure to ourselves, that probably 

 10 or 15 gallons of blood are thrown out at one stroke, and moved with an 

 immense velocity through a tube of a foot diameter^ the whole idea fills the mind 

 with wonder. The veins I believe have nothing particular- in their structure, 

 excepting in parts requiring a peculiarity, as in the folds of the skin on the 

 breast in the piked whale, where their elasticity was to be increased. 



