530 GENERAL DISEASES. 



chest is a prominent feature. Death may also quickly occur from 

 continued spasm of the muscles of the larynx. The symptoms gene- 

 rally come on gradually. Although there is continued cramp of the 

 muscles; the patient suffers from aggravated spasms from time to 

 time, the slightest noise or excitement being frequently sufficient 

 to bring them on. The bowels are constipated, and there is often 

 retention of urine, from the horse being unable to stretch himself 

 out. In very mild cases the animal may be able to lie down. As 

 a rule, the patient preserves his desire for food and drink ; but is 

 unable to gratify it, except to a very small extent, owing to the 

 rigidity of his chewing and swallowing muscles. 



"Recovery is rare before the third week. Generally about this 

 time, the muscular contraction begins to decrease; the appetite im- 

 proves; the breathing becomes calmer; and the movements easier. 

 Very often the change for the better does not set in before the end 

 of the fifth or sixth week ; and the improvement continues through 

 a long period of uneasiness, rigidity of movement, and stiffness of 

 the spinal column [from the head to the tail]. Convalescence is 

 long, and is often protracted for several months" (Friedherger 

 and Frdhner). 



IMMUNITY AND PROTECTIVE INOCULATION.— Horses may be 

 made immune from tetanus for a short time by one attack of this dieeare, or 

 by injecting, at first, extremely small doses of the tetanus poison, and 

 gradually increasing it tO' a very large amount, which can be done, later on, 

 without the animal becoming affected. This process of protective inoculation 

 could be carried out only under the direction of a capable bacteriologist. 



The immunity conferred by an attack of tetanus, appears to be of short 

 duration. Mr. Sidney Villar,' F.R.C.V.S. tells us (" Journal of Comp. Path." 

 Dec. 1897) that he " treated a black filly which recovered from an attack in 

 September, but again fell a victim to the disease in the following July." 



We have seen in Chapter III. that protection can be obtained by injecting 

 immune serum at the time of, or shortly after, infection. The action of the 

 serum is limited to destroying (or neutralising) the toxins which are in the 

 blood and tho5e which are being manufactured by the bacilli that are located 

 in or near the wound ; but the serum has no neutralising eifeet on the toxins 

 which have become fixed in the brain (Carouofeau). Hence, the longer its 

 application is delayed, the less efficacious will it be. In places where 

 tetanus is common, it is evidently wise to use protective inoculation against 

 this disease in cases of wounds which, like those of castration, punctured 

 feet, &c., are, under ordinary circumstances, frequently followed by tetanus, 

 and which cannot be treated antiseptically. There should, as we have 

 seen, be no delay in applying this means of protection. Nocard recommends an 

 injection of about ^^ oz. (20 cubic centimetres) of immune serum under the loose 

 skin of the neck or shoulder, and repeated after an interval of a fortnight. The 

 period of immunity obtained from the injection of anti-toxin serum, is more or 

 less proportionate to the dose, and lasts from a fortnight to six weeks. It can, 

 however, be prolonged indefinitely by successive injections. 



PREVENTIA^E TREATMENT.— The remarks already made about 

 the microbe of tetanus will show the necessity of treating wounds, as 

 far as we can, antiseptically (p. 67), especially in places where this 

 disease is common. Although the spores of tetanus are but little 



