METHODS OF INOCULATION 695 



If symptoms of collapse appear during a subdural injection, they may 

 be relieved by allowing the fluid within the canal to flow out again, and 

 this is best accomplished when the inoculation is given by the gravity 

 method. The latter method has been largely worked out and is highly 

 recommended by Sophian, these recommendations being based upon 

 his extensive experience in the recent Texas epidemic of cerebrospinal 

 meningitis. It is also recommended by Flexner and the Hygienic 

 Laboratory, and is undoubtedly the method of choice. 



Blood-pressure as a Guide in Administering Serum Subdurally. 

 According to the older and customary method of injecting serum sub- 

 durally, fluid is permitted to flow from the needle until from 15 to 20 

 c.c. have been removed, and an equal quantity of serum is then injected. 

 In severe cases, with thick plastic exudates, only a few cubic centimeters 

 of fluid may be withdrawn, and, indeed, no fluid at all may be secured. 

 To inject arbitrarily a fixed amount of serum under such conditions may 

 be highly dangerous to the patient, on account of increased pressure. 

 On the other hand, when the flow is free, it may be dangerous to permit 

 the canal to drain until intraspinal pressure is reduced to the normal, a 

 fact indicated by the flow of a drop of fluid every three to five seconds. 



With these considerations in mind, Sophian 1 has studied the value 

 of cerebrospinal fluid pressure and blood-pressure as controls on the 

 amount of fluid that may be safely withdrawn and on the amount of 

 serum that may be injected. During the study and treatment of 500 

 cases of epidemic cerebrospinal meningitis this last-named observer 

 found that the blood-pressure was a valuable guide. Cerebrospinal 

 fluid pressure was found to be misleading, owing probably to a local dis- 

 tention of the subarachnoid space at the site of injection, which resulted 

 in readings that did not represent the true intracranial pressure. 



1. Usually, upon the withdrawal of cerebrospinal fluid, a fall of 

 blood-pressure occurs. With the ordinary blood-pressure in an adult 

 patient about 110 mm. of mercury Sophian recommends stopping 

 the flow when there has been a drop in pressure of about 10 mm. of 

 mercury; in children, about 5 mm. In a few cases there is no change 

 in blood-pressure or even a slight rise; in these instances fluid may be 

 removed until the flow has diminished to the rate of a drop every three 

 to five seconds. 



2. With the injection of serum the blood-pressure drops still further. 

 Generally, the decrease in blood-pressure is proportional to the rapidity 

 with which the serum is injected and the amount injected. By the 



1 Epidemic Cerebrospinal Meningitis, 1913, Mosby Co., St. Louis. 



