58 The Prccipitins: Method* 



proceed to empty the syringe, slightly retracting the point if there 

 appears to be any impediment to the outflow. After the injection has 

 been made, and the needle withdrawn, the parts are dried, and tincture 

 of benzoin is applied, sealing the small opening made by the scalpel 

 (usually but 1'5 2 mm. long). The wound usually heals by first 

 intention, the animal experiencing no discomfort. In this way I have 

 repeatedly injected animals in the same region, all the punctures made 

 during the treatment being included within the area shaved as stain I 

 above. It will be seen that the operation is exceedingly simple, and 

 I should not describe it but for the fact that many do not know how to 

 perform it. 



Intravenous Injections. 



Intravenous injection is practised by introducing a fine-needled 

 syringe into the marginal ear-vein, and injecting smaller quantities 

 than in the preceding method, for the reason, not only that they suffice, 

 but that much smaller doses exert a toxic action when introduced 

 intravenously as against intraperitoneally. Intravenous injections are 

 very easily practised after a little experience. Before introducing the 

 needle the skin of the ear should be shaved and disinfected as in the 

 preceding case. 



Subcutaneous injections arc not to be recommended from my 

 experience. Absorption of injected material takes place more slowly 

 this way than through the peritoneum, and the mechanical effects of 

 large injections are liable to lead to sloughing. 



Marking the Rabbits. 



It is absolutely essential that there should be no confusion amongst 

 the animals treated, especially where these arc at all numerous. The 

 best way to secure this is to tattoo the rabbits inside the ear. This is 

 easily done by dipping a fairly large needle into India-ink and pricking 

 it through the skin, a proceeding which the rabbit does not appear to 

 mind. Various letters and simple signs can be made in this way, and 

 there is then no possibility of confusing the animals. 



Weighing the Animals. 



It is desirable to weigh the animals during treatment. I have 

 always done this before each injection, stopping treatment as a rule 

 when a notable fall in weight occurred. I have had less loss in weight 



