438 IMMUNITY. 



a single large dose. Later, when large doses of toxine 

 injected subcutaneously are well borne, the toxine is injected 

 directly into the jugular vein of the animal. Ultimately 

 300 c.c., or more, of active diphtheria toxine thus injected 

 may be borne by a horse, such a degree of resistance being 

 developed after the treatment has been carried out for two 

 or three months. In all cases of immunising, the general 

 health of the animal ought not to suffer. If the process is 

 pushed too rapidly, the antitoxic power of the serum may 

 diminish instead of increasing and a condition of marasmus 

 may set in and may even lead to the death of the animal. 

 (In immunisation of small animals an indication of their 

 general condition may be obtained by weighing them from 

 time to time.) 



Up till recently, the preparation from a horse of an 

 antitoxic serum of high value involved very prolonged treat- 

 ment, usually lasting for eight or ten months. Cartwright 

 Wood has, however, devised a method by which the 

 period of immunisation is much shortened, and which 

 promises to give serum of very high antitoxic powers. In 

 this method he uses two " toxines." The one is the 

 ordinary toxine obtained from bouillon cultures as above 

 described, which is believed to contain the ferments ; the 

 other is obtained by growing the diphtheria bacillus in a 

 mixture of bouillon and 20 per cent of blood serum (the 

 latter is prevented from coagulating by having its lime salts 

 precipitated by oxalic or citric acid). Such a culture when 

 filtered contains the ferments along with a large proportion 

 of albumoses, produced by the action of the bacillus on the 

 albumin. The ferments are destroyed by exposure to 

 65 C. for an hour, and the fluid is then known as " serum 

 toxine" in centra-distinction to the ordinary "broth toxine." 

 The serum toxine gives rise to little local irritation but to 

 marked febrile reaction. By its use the early period of 

 immunisation is much shortened, so that a horse can tolerate 

 a large dose of ordinary broth toxine in a shorter time than 

 was formerly possible ; and by combining its use with that 

 of broth toxine a serum of remarkably high antitoxic powers 



