322 BACTERIA. 



dry heat, he filled it to the depth of three-quarters of an 

 inch, or an inch with some hygroscopic material such as 

 solid potassium hydrate ; it was then ready for use. 



A rabbit was previously inoculated in the following 

 manner : The skin over the part of the skull covering the 

 brain is carefully saturated with a 5 per cent, solution of car- 

 bolic acid. (This serves two purposes : first, it purifies the 

 skin through which the knife is to pass, and, secondly, it 

 renders the skin and the tissues beneath perfectly insensible 

 to pain, so that the rabbit will remain perfectly quiet while 

 the operation goes on ; it does not apparently suffer even 

 discomfort, and I have seen a rabbit going on eating whilst 

 the operation was being performed. I have also seen the 

 operations performed as in the Pasteur Institute, while the 

 animal was under the influence of chloroform ; but I have 

 never yet seen it done without either a local or a general 

 anaesthetic being administered). An incision is made through 

 the insensitive tissues so as to give either a cruciform incision 

 or a semi-circular flap, the soft tissues are dissected from the 

 bone, and then with a small tube with teeth at the end, and 

 a sliding pin in the centre (a trephine), a little circular disc 

 of bone is removed, as far as possible without injuring the 

 external covering membrane of the brain. 



With a subcutaneous injection syringe, carefully purified 

 by means of some chemical germicidal reagent, or heat, a very 

 minute quantity of the cerebro-spinal fluid, taken from an 

 animal that has succumbed to the disease, is then injected 

 under the dura-mater (the membrane above mentioned), 

 which is immediately beneath the bone of the skull. The 

 disc of bone is then replaced ; the wound is closed by means 

 of a couple of stitches ; a pad of cotton wadding, carefully 

 purified by heat, is used to dry the skin as much as possible ; 

 after which a little of the same cotton wadding is used as a 

 dressing ; this dressing is kept in position by a free ap- 

 plication of flexile collodion, the two together forming an 

 air proof shield, through which no organisms from the 

 external air can make their way to the wound, which, as 

 a rule, heals up most perfectly in less than a couple of 

 days. The operation does not appear to affect the animal 

 so treated in the slightest, and until the seventh day it 

 appears to be as lively as any of its companions ; it then 

 gradually begins to lose the power of the muscles, first 



