THE CIRCULATING LIQUIDS OF THE BODY 57 



irritated. The first effect of irritation is an increase in the 

 flow of blood through the affected region. If the irritation 

 continues, or if it was originally severe, the current soon 

 begins to slacken, the corpuscles stagnate in the vessels, and 

 inflammatory stasis is produced. The leucocytes adhere in 

 large numbers to the walls of the capillaries, and particularly 

 of the small veins, and then begin to pass slowly through 

 them by amoeboid movements, the passage taking place at 

 the junctions between, or it may be through the substance 

 of, the endothelial cells. Plasma is also poured out into the 

 tissues, the whole forming an inflammatory exudation. 

 Even red blood-corpuscles may pass out of the vessels in 

 small numbers. The exudation may be gradually reabsorbed, 

 or destruction of tissue may ensue, and a collection of pus 

 be formed. The cells of pus are largely, if not entirely, emi- 

 grated leucocytes. 



PRACTICAL EXERCISES ON CHAPTER I. 



N.B. In the following exercises all experiments on animals which 

 would cause pain are to be done under complete ancesthesia. 



1. Reaction of Blood. With a clean suture-needle prick one of the 

 fingers behind the nail. Bandaging the finger with a handkerchief 

 from above downwards, so as to render its tip congested, will often 

 facilitate the getting of a good-sized drop. Put a drop of blood on 

 a piece of glazed neutral litmus paper ; wash off in 10 to 30 seconds 

 with distilled water. A blue stain will be left, showing that fresh 

 blood is alkaline. 



2. Specific Gravity of Blood (i) Hammerschlag s Method. Put a 

 mixture of chloroform and benzol of specific gravity ro6o into a small 

 glass cylinder. Obtain a drop of blood as in i. Put it in the mixture 

 by means of a small pipette. If it sinks, add chloroform, if it rises, add 

 benzol, till it just remains suspended when the liquid has been well 

 stirred. Then with a small hydrometer measure the specific gravity 

 of the mixture, which is now equal to that of the blood. Filter the 

 liquid to free it from blood, and put it back into the stock-bottle. 

 This is a convenient method, but some prefer 



(2) Roy's Method. Take 25 small bottles containing mixtures of 

 glycerine and water of specific gravity 1-027, 1*029 . . . 1-070. 

 Begin with bottle 1*059. Pour a- little of the liquid into a small 

 vessel. Then prick the finger with a sharp, clean suture-needle, and 

 suck up a small drop of blood into the horizontal limb of a capillary 

 tube with a rectangular elbow. Immerse the horizontal part of the 

 tube in the glycerine mixture, and gently blow the drop of blood into 



