14 THE BLOOD. 



the lymph, chyle, and blood ; and, finally, it has been shown that all of these bodies, 

 which were formerly supposed to present marked distinctive characters, belong to the 

 same class, presenting but slight differences in different situations. The description which 

 will be given of the white corpuscles of the blood, and the effects of reagents, will an- 

 swer, in the main, for all the corpuscular bodies that are grouped under the name of 

 leucocytes. 



Leucocytes are normally found in the blood, lymph, chyle, semen, colostrum, and 

 vitreous humor. Pathologically, they are found in the secretion of mucous mem- 

 branes, following irritation, and in inflammatory products, when they are called pus- 

 corpuscles. 



In examining a specimen of blood with the microscope, we immediately notice the 

 marked difference between the leucocytes and red corpuscles. The former are globular, 

 with a smooth surface, somewhat opaque from the presence of more or less granular 

 matter, white, and larger than the red corpuscles. 



In examining the circulation under the microscope, we are struck with the adhesive 

 character of the leucocytes as compared with the red corpuscles. The latter circulate 

 with great rapidity in the centre of the vessels, while the leucocytes have a tendency to 

 adhere to the sides, moving along slowly, and occasionally remaining for a time entirely 

 stationary, until they are swept along by a change in the direction or force of the 

 current. 



The size of the leucocytes varies somewhat, even in any one fluid, such as the blood. 

 Their average diameter may be stated as -g^sif f an m ch. It is in pus, where they exist in 

 greatest abundance, that their microscopical characters may be studied with greatest ad- 

 vantage. In this fluid, after it is discharged, the corpuscles sometimes present remarkable 

 deformities. They become polygonal in shape, and sometimes ovoid, occasionally presenting 

 projections from their surface, which give them a stellate appearance. These alterations, 

 however, are only temporary; and, after from twelve to twenty-four hours, they resume 

 their globular shape. On the addition of acetic acid, they swell up, become transparent, 

 with a delicate outline, and present in their interior one, two, three, or even four rounded, 

 nuclear bodies, generally collected in a mass. This is rather to be considered as a coagu- 

 lation of a portion of the corpuscle, than a. nucleus brought out by the action of the acid 

 which renders the corpuscle transparent ; although in some corpuscles it is seen without 

 the addition of any reagent. This appearance is produced, though more slowly, by the 

 addition of water. 



Leucocytes vary considerably in their external characters in different situations. 

 Sometimes they are very pale and almost without granulations, while at others they are 

 filled with fatty granules and are not rendered clear by acetic acid. As a rule, they 

 increase in size and become granular when confined in the tissues. In colostrum, where 

 they are called colostrum-corpuscles, they generally undergo this change. As the result 

 of inflammatory action, when they are sometimes called inflammatory or exudation-cor- 

 puscles, leucocytes frequently become much hypertrophied and are filled with fatty 

 granules. 



The deformation of the leucocytes, to which allusion has already been made, is some- 

 times so rapid and changeable as to produce creeping movements, due to the projection 

 and retraction of portions of their substance. These movements are of the kind called 

 amo3boid, and are supposed to be important in the process of migration of the corpus- 

 cles, which has lately been described. 



The quantity of leucocytes compared to the red corpuscles can only be given approxi- 

 matively. It has been estimated by counting under the microscope the red corpuscles and 

 leucocytes contained in a certain space. Moleschott gives the proportion as 1:335; 

 others, at from 1 : 300 to 1 : 500. It has been found by Dr. E. Hirt, of Zittau, whose 

 observations have been confirmed by others, that the relative quantity of leucocytes 

 is much increased during digestion. He found, in one individual, a proportion of 1 : 1800 



