Securing Blood from Animals 273 



readily, and through it, from time to time, a capillary pipet 

 can be introduced and the fluid withdrawn. 



Small animals, such as rabbits and guinea-pigs, can be 

 held in the hand, as a rule. Guinea-pig and rabbit-holders 

 of various forms can be obtained from dealers in laboratory 

 supplies. The best of these is undoubtedly that of Latapie, 

 shown in the accompanying illustration (Fig. 75). Dogs, 

 cats, sheep, and goats can be tied and held in troughs. A 

 convenient form of mouse-holder, invented by Kitasato, is 

 shown in figure 77. 



In all these experiments one must remember that the 

 amount of material introduced into the animal must be in 

 proportion to its size, and that injection experiments upon 

 mice are usually so crude and destructive as to warrant the 

 comparison drawn by Frankel, that the injection of a few 

 minims of liquid into the pleural cavity of a mouse is " much 

 the same as if one would inject through a fire-hose three or 

 four quarts of some liquid into the respiratory organs of a 

 man." 



Method of Securing Blood from Animals. For many 

 experimental purposes it becomes necessary to secure blood 

 in larger or smaller quantities from animals. For horses, 

 cattle, calves, goats, sheep, large dogs, etc., this is a simple 

 matter, all that is necessary being to restrain the animal, 

 make a minute incision in the skin over the jugular vein, 

 which is easily found by compressing it at the root of the 

 neck and noting where the vessel expands, and introducing 

 a canula when the vein is well distended. The trocar being 

 withdrawn, the blood at once flows. A sterile tube is 

 slipped over the cannula and the blood conducted into a 

 sterile bottle or flask. 



For rabbits and guinea-pigs the technic is rather more 

 difficult because of the smaller size of the vessels. Drops 

 and small quantities of blood may be secured by opening 

 one of the ear veins, but when any quantity of blood is 

 required, the neatest operation is done by tapping the 

 common carotid artery by the method employed at the 

 Pasteur Institute at Paris. 



The animal is restrained in a Latapie holder, with the 

 neck extended. Anesthesia can be used, but must be em- 

 ployed with great care. The hair on the front of the neck 

 is clipped and the neck shaved, or, as is easier, the hair is 

 18 



