670 INFECTIOUS DISEASES. 



of skin. On the fifth day exudation commences, and from the sixth to 

 the seventh day a large quantity of vaccine lymph may be collected. 

 The line of inoculation appears slightly umbilicated and surrounded 

 by a greywish-white zone and a hard peripheral swelling. 



Vaccine may be collected from the fifth day in summer to the 

 eighth day in winter. 



The inoculated area having been cleansed with boiled water and 

 carefully dried, the little crusts covering the inoculation wounds are 

 loosened and the wounds themselves gently scraped with a special 

 curette of small size. The exuded liquid is very active. 



The base of each swelling is then grasped in a little special clamp, 

 which acts like a pressure forceps and causes the discharge of a further 

 large quantity of active vaccine lymph. All the material thus obtained 

 is mixed ; an equal quantity of neutral glycerine is added, the whole 

 is finely triturated, passed through a cloth, and stored in little sterilised 

 glass tubes, which are hermetically sealed. 



The vaccine thus prepared retains its activity for from five to eight 

 months, if kept from the action of heat and light. Accidental germs 

 which may have developed in the wounds and thus gained entrance 

 to the vaccine gradually lose their activity. After from forty to sixty 

 days the vaccine may be regarded as absolutely pure and incapable 

 of producing accidental suppuration, as sometimes occurs when fresh 

 vaccine is employed. 



The old electuaries, dried vaccines, vaccine pastes, etc., have been 

 almost entirely given up, the above method always yielding a pure 

 and active vaccine. Vaccination with calf lymph should always be 

 preferred to vaccination from arm to arm, in view of possible trans- 

 mission of grave disease, such as syphilis. 



TETANUa 



Tetanus is a disease characterised by tonic contraction of the 

 muscles of one or more limbs or of all the muscles of the body. 



Causation. It is due to the growth of Nicolaier's bacillus in some 

 part of the body (in accidental wounds, in the uterine cavity after 

 parturition, etc.), and the contraction of muscles is due to toxins 

 (elaborated by the microbe), which have a selective affinity for the 

 nervous centres. 



These toxins, secreted by bacilli localised in wounds, are absorbed 

 and carried away by the lymphatic and vascular channels and dis- 

 tributed throughout the body. They seem chiefly to affect the cells of 

 the central nervous system. Infection is due to microbes capable of 

 living as saprophytes outside the animal body. 



