156 TEXT-BOOK OF BACTERIOLOGY. 



Similar to the subcutaneous inoculation is a special kind of in- 

 oculation, the introduction of the material into the anterior cham- 

 ber of the eye. It was first employed by Cohnheim and Salo- 

 monsen. It is extremely well calculated to yield information as to 

 the special symptoms in the course of a disease, and is therefore of 

 great value. It is performed by treating the eyeball with cocaine^ 

 pressing 1 it forward out of its socket, and then making an incision 

 from above, at the junction of the cornea and sclera. Some of the 

 aqueous humor flows out, and when this has taken place the virus 

 is introduced through the incision. 



Essentially different from simple inoculation and from subcu- 

 taneous application is the process by which bacteria are brought 

 directly into the blood-vessels, and thus at once enabled to spread 

 through the entire organism. For this purpose we endeavor to 

 open one of the large veins and introduce the substance for inocu- 

 lation into the circulating stream, by means of a syringe. We 

 either expose the jugularis communis or externa, or, what is much 

 easier, we take, in the case of larger animals such as rabbits, one 

 of the veins of the ear, the best being the one that runs along the 

 exterior edge of the ear. With the canula of the syringe we pierce 

 the blood-vessel and inject the virus into it, either directly through 

 the skin or, if necessary, after cutting through the surrounding 

 tissue, and after having compressed the vein below the point 

 selected for puncture, so as to make it swell as much as possible. 

 The virus must of course be applied in the form of a liquid solution. 

 It requires some practice. Beginners find that the elastic walls of 

 the veins are very apt to slip under the hand, in which case the 

 inoculating fluid is injected into the subcutaneous cellular tissue, as 

 may be plainly seen by the appearance of a thick lump near the 

 vein, which never occurs after a successful injection. 



If we desire to give the virus a particularly wide distribution, 

 we inject directly into the large cavities of the body. We pierce 

 the thoracic or peritoneal cavity with the canula and inject the 

 material. The danger of injuring the intestines or one of the 

 larger vessels is not great, as these flexible parts usually slip out of 

 the way of the syringe. 



Yet we must never forget how serious a matter such an opera- 

 tion is, even in the best of cases. We know well, from human 

 pathology, that the serous linings of the thoracic and abdominal 

 cavities are exceedingly sensitive to injuries of all kinds, and there- 

 fore we cannot be too cautious in drawing conclusions from results 

 obtained in this manner. Only in a restricted sense can we here 

 speak of infectious processes, properly so called, since in the great 



