50 STUDIES IN ADVANCED PHYSIOLOGY. 



elements containing haemoglobin, no doubt identical with 

 blood corpuscles, do really occur. It is a matter of interest 

 that coloring matters other than haemoglobin occur. Thus 

 in the cuttlefish, some snails, and the lobster, a bluish com- 

 pound containing traces of copper, called hsemocyanin, 

 colors the blood. 



The white corpuscles are distributed throughout the blood 

 of the invertebrate world. When we come to the verte- 

 brated or back-boned animals, there are in addition to these 

 white corpuscles, the red ones. The lowest vertebrate 

 animal (amphioxus), however, possesses no red corpuscles. 



AMOUNT. * 



The amount of blood in the human body has been esti- 

 mated by a number of observers to be about one-thirteenth 

 of the weight of the body, thus making for the average 

 person from twelve to fifteen pounds of blood, and calcu- 

 lating a pound of blood to measure about a pint, would 

 give us in the neighborhood of one and one-half gallons of 

 this fluid. This amount of blood is at any one time dis- 

 tributed as follows: One-fourth of it is in the heart and 

 the neighboring large blood vessels, one-fourth of it is 

 found in the liver, one-fourth in the capillaries of the vol- 

 untary muscles, the remaining one-fourth being distributed 

 over the rest of the. body. If fresh blood drawn from the 

 veins or arteries of an animal be allowed to run into a 

 vessel and there prevented from clotting, in a way to be 

 noted later, the suspended particles or corpuscles being a 

 little heavier than the liquid, sink to the bottom and occupy 

 about fifty per cent, of the volume in their wet condition. 

 Examination of these solid particles of the blood reveals 

 two kinds of corpuscles one the red corpuscle already 

 mentioned, the other the colorless corpuscle, sometimes 

 called lymph corpuscle or leucocyte. The existence of a 

 third corpuscle, that of the placques or blood tablets, as 

 a distinct structure, is questioned by some physiologists, 

 and a further discussion of this element of the blood is 



