PREVENTIVE MEDICINE 327 



disease showing itself either as a passing indisposition or less 

 frequently by symptoms of nervous excitability followed by para- 

 lysis and death. During recent years Stockman has studied the 

 disease and gone a long way towards clearing up many obscure 

 points with regard to its natural transmission, &c. As to its 

 etiology, Stockman has demonstrated the existence of " chromatin 

 bodies " resembling protozoa in certain lymphatic glands and in the 

 blood of affected sheep and, so far as can be said at present, it 

 seems to be probable that these bodies are the actual parasites of 

 the disease. Louping-ill can be transmitted to healthy sheep by 

 the inoculation of blood and lymphatic gland juice containing these 

 bodies, and natural transmission occurs by means of ticks (Ixodes 

 ricinus). Stockman has transmitted the disease to healthy sheep 

 by means of adult and larval ticks which in their previous stages 

 had fed on animals affected with louping-ill, and thus the infective 

 agent has been proved to pass through the egg. The blood of a 

 recovered sheep is no longer infective by inoculation, but such an 

 animal has a considerable degree of immunity. The disease occurs 

 on certain farms, so-called " louping-ill farms," and has a definite 

 seasonal incidence, chiefly April, May and early June, and less in 

 autumn, while a few cases are seen at any time of the year. 



PREVENTIVE MEASURES. It is difficult at the moment to suggest 

 really practical measures to be put into operation against louping- 

 ill since some points in the epizootiology of the disease are still 

 obscure. Since the disease is tick-borne, however, it is obvious that 

 one of the chief problems is the destruction of infected ticks. 

 It is likely that the incidence of the disease may be considerably 

 lessened by heavily stocking infected pastures, and dipping fre- 

 quently, e.g., at 5 day intervals. 



Such measures should be put into operation during the louping- 

 ill seasons as it is at this time of the year that one is most likely 

 to catch the largest number of ticks. 



FELINE DIPHTHERIA. 



This disease is described by H. Gray* as " a contagious one of 

 the cat, characterised by the presence of diphtheritic membranes 

 on the fauces, pharynx or larynx, and due to some micro-organism 

 not yet determined." 



Though no connection between feline and human diphtheria 

 has been proved, it would nevertheless be advisable to strictly 

 isolate cats showing symptoms of the disease, and owing to the 

 * Wallis-Hoare, System. Vet. Med., 1913, Vol. I., p. 317. 



