LECT. VII. COMPOSITION OF THE BLOOD. 135 



tail this modification of the blood. Which of the or- 

 ganic elements of the blood undergoes this change ? In 

 what does it chemically consist ? If I must reply with 

 precision to these questions, I admit that hitherto experi- 

 ments made for the purpose of solving them, have thrown 

 very little light on the subject, and I can only select, from 

 amongst an immense number of experiments, those which 

 appear generally to be the least imperfect and the least 

 discordant. 



Composition of the Blood. Micrographers now define 

 the blood to be a liquid chiefly composed of water, in 

 which are dissolved various salts, albumen, fibrine, and 

 fatty bodies ; and in which is suspended a great number of 

 red globules, having a definite form, and whose diameter 

 is greater or less in different animals. These globules are 

 analogous to a vesicle where the coloured involucre is solu- 

 ble in acetic acid.* I will show you a beautiful experi- 

 ment of Miiller, which will give you a correct idea of the 

 composition of the blood. 



I puncture the hearts of a number of living frogs, and 

 receive the effluent blood on a paper filter. There flows 

 through the paper a yellowish liquid, while the red glo- 

 bular matter remains on the filter. In a few moments 

 the filtered liquid coagulates and yields a clot composed 

 of fibrine. Thus we see, on one side, the colouring mat- 

 ter, and on the other, the serum wherein the fibrine was 

 dissolved. If the blood had not been filtered, the fibrine 



* The globules, or more correctly the corpuscles, of the blood are be- 

 lieved to consist of three parts; 



1. A capsule, shell, envelope, or involucre, composed of an albumi- 



nous substance sometimes called globulin. 



2. A nucleus. 



3. An intermediate red colouring matter, apparently in a fluid state 

 and called h&matin or h&matosine. J. P. 



