270 MICEOBES, FERMENTS, AND MOULDS. 



be necessary and sufficient, quantities which vary 

 according to circumstances. In order to vaccinate 

 a sheep against anthrax, the animal must be held by 

 its fore feet in a sitting position, so as to present its 

 belly to the operator ; the tube of a Pravaz syringe, 

 containing the injection, is then inserted in the base 

 of the groin, which is devoid of wool. In cattle the 

 operation is performed at the root of the tail. It is 

 performed twice first with a weak vaccine, and, after 

 the lapse of a week, with one which is stronger. 



Every one is acquainted with the process of vacci- 

 nating the human subject against small-pox, which 

 may be done either with lymph from an infant or 

 from a calf. A lancet or grooved needle is employed, 

 on which there is a drop of lymph, and five or six 

 punctures are made on the arms or thighs. 



We must not imagine that vaccination can become 

 an absolute preservative from all diseases. For in- 

 stance, in erysipelas, pneumonia, and gonorrhoea 

 a first attack is so far from warding off a second 

 attack of the same disease, that it creates a favourable 

 field for relapses. It may, consequently, be assumed 

 a priori that vaccination in such cases would do more 

 harm than good (Cornil). It is the same with inter- 

 mittent fever, tuberculosis, syphilis, etc. ; all diseases 

 by which the same individual may be attacked several 

 times, and at varying intervals of time a clear proof 

 that the first attack has created no immunity against 

 subsequent attacks. 



