222 



BACTERIOLOGY. 



has led me to prefer a syringe after the pattern of C, 

 in Fig. 45 i. e., the form commonly used by physi- 

 cians. The reason for this is as follows : in making 

 injections, either into the circulation or under the skin, 

 there is a certain amount of resistance to the passage of 

 fluid from the needle. If one overcomes this resistance 

 by means of a cushion of compressed air, as is the case 

 in syringes A and B y Fig. 45, the sudden expansion 

 of the air in the body of the syringe when resistance is 

 overcome frequently causes a larger amount of fluid to 

 be injected than is desired. No such accident is likely 



PIG. 45. 



Forms of hypodermic syringe. 

 A. Koch's syringe. B. Syringe of Strohschein. C. Overlack's form. 



to occur when the fluid is forced from the barrel of the 

 syringe by the head of a close-fitting piston, with no air 

 intervening between the fluid and the head of the piston. 

 With such an instrument, properly manipulated, the 

 dose can always be controlled with accuracy. 



INOCULATION INTO THE LYMPHATIC CIRCULATION. 

 Fluid cultures or suspensions of bacteria may be in- 

 jected into the lymphatics by way of the testicles. The 

 operation is in no wise complicated. One simply plunges 

 the point of the hypodermic needle directly into the sub- 



