72 MICROSCOPIC EXAMINATION OF THE BLOOD. 



The size varies equally with the form. In amphibia they 

 are regarded as the largest; in birds and fishes next in 

 size, and in mammalia smallest. The human globules are 

 about one-fourth the size of those of the frog. They are 

 larger in the embryo than the adult, and are made to 

 measure from the 1-5000 to the 1-3000 of an inch, though 

 the size often varies. The globules or corpuscles of the 

 frog show, under the microscope, that their structure con- 

 sists of a membranous envelope thin, transparent and 

 vesicular enclosing a nucleus, seemingly solid, and having 

 the colored matter surrounding this nucleus and placed 

 between it and the envelope. The nucleus is regarded as 

 about one-third of the length of the corpuscle. The envel- 

 ope is found to be highly elastic, and both it and the col- 

 oring matter are considered to be quite soft and yielding in 

 their nature. 



The structure of the human globule is believed by some 

 to have a similar envelope, nucleus and coloring substance, 

 as in the frog, though others consider it extremely ques- 

 tionable whether the blood corpuscle in man, or any of the 

 mammalia, have any nucleus at all, and are therefore dis- 

 posed to deny its existence in these animals. The nucleus 

 is generally seen in the centre of the corpuscle. Besides the 

 red corpuscle, there is another kind called the pale or color- 

 less corpuscle. These are found to be fewer in number, 

 larger, and to vary less in size and shape than the red. As 

 their name implies, they are destitute of color and specifi- 

 cally lighter than the red. 



The globules are suspended in the liquor sanguinis, their 

 natural fluid, without alteration. Water dissolves the col- 

 oring matter, leaving the nucleus; acetic acid changes the 

 form as well as dissolves the coloring matter; and liquor 

 potassse dissolves both coloring matter and nucleus. 



Thus the blood is seen to consist of many chemical and 

 microscopical elements, each and all of which are adapted 

 the one to the other, in precise and definite proportions, to 

 constitute health ; and to add to, abstract from or alter in 

 any way the natural relation between any two or more, 



