BLOOD.] PHYSIOLOGY, 49 



it is called, is still liquid ; you will find it hard work if 

 you try to cut it with a knife. The white of the hard 

 boiled tgg^ on the other hand, is quite solid, and you 

 can cut it into ever so .thin slices. It has been " set " 

 by boiling. Well, the serum of blood is in this respect 

 very like white of egg. In fact they both contain the 

 same substance, called albumin, which has this 

 property of " setting " or becoming solid when heated 

 nearly to boiUng-point. Both the serum of blood 

 and white of ^%g even when " set '' are wet, Le. contain 

 a great deal of water. You may dry them in the 

 proper manner into a transparent horny substance. 

 When quite dry they will readily burn. They are 

 therefore things which can be oxidized. When burnt 

 they give off carbonic acid, water, and ammonia ; the 

 latter you might easily recognize by its effect on your 

 nose if you were to burn a piece of dried blood in a 

 flame. Now, when I say that albumin in burning 

 gives off carbonic acid, water, and ammonia, you 

 know from your Chemistry that it must contain car- 

 bon to form the carbonic acid, hydrogen to form 

 water, and nitrogen to form ammonia. It need not 

 contain oxygen, for as you know it could get all the 

 oxygen it wanted from the air; still it does contain 

 some oxygen. Albumin, then, is an oxidizable 

 or combustible body made up of nitrogen, 

 carbon, hydrogen, and oxygen. It is important 

 you should remember this ; but I will not bother you 

 with how much of each — it is a very complex, sub- 

 stance, built up in a wonderful way, far more complex 

 than any of the things you had to learn about in your 

 Chemistry Primer. And this albumin, dissolved in 



a great deal of water, forms the serum of blood. 



P 31 .,.- 



:s 



