]92 



BACTERIOLOGY. 



however, by continuing the injection, when the circu- 

 lation of clear fluid through the vessels will not only 

 fail to take the place of the circulating blood but 

 there will at the same time appear a localized swelling 

 under the skin about the point of the needle. The 

 needle must then be withdrawn and inserted into the 

 vessel at a point a little nearer to its proximal end. 



Care must be taken that no air is injected. 



The hypodermatic syringe and needle must, previous 

 to operation, have been carefully sterilized in the steam 

 sterilizer. The animal must be kept under close observa- 

 tion for about an hour after injection. 



Fig. 38. 



Forms of hypodermatic syringe. 

 A, Koch's syringe ; B, syringe of Strohscheln ; C, Overlack's form. 



The form of syringe best suited for this operation is 

 of the ordinary design, but one that permits of thorough 

 sterilization by steam. It should be made of glass and 

 metal, with asbestos packings. The syringes commonly 

 employed are those shown in Fig. 38 — A, Koch's; B, 

 Strohschein's ; C, Overlack's. 



