232 IMMUNO-CATALYSIS 



testicle extract induces a general increase in permeability of the skin 

 with a correspondingly increased susceptibility of the skin to infectious 

 agents. 



The Duran-Reynals effect was observed on the enhancement of 

 staphylococcal infection by the presence of testicular extract with the 

 infective dose (Duran-Reynals and Suner-Pi, 1928). Pijoan (1931) 

 found that the extracts from testicle, kidney, and spleen enhanced the 

 infective power of 20 strains of various bacteria to a high degree. 

 Hoffmann (1931) reported that this factor promoted the pathogenic 

 action of the viruses of herpes, vesicular stomatitis of horses, Borna 

 disease, and vaccinia. Favilli (1931) reported that testicle extract 

 caused notable fragility of red blood cells in vitro. It was reported 

 that this factor obtained from the testicles of rat, rabbit and bull pre- 

 vents or retards the growth of a rabbit tumour when a mixture of the 

 extract and a tumour cell suspension is inoculated intradermally 

 (Duran-Reynals, 1931). Boyland and McClean (1935) reported that 

 aqueous extracts of rapidly growing grafted mammalian tumours con- 

 tain a factor which, on intracutaneous injection into the rabbit, 

 increases the permeability of the dermis. The rate of the growth of the 

 tumour was stated to be a measure of the amount of the factor pres- 

 ent. Duran-Reynals (1933), pointed out that this factor is present 

 in the filtrates of virulent strains of pneumococci and streptococci. 



Following the demonstration by Duran-Reynals that bacterial fil- 

 trates contain a factor similar to that extracted from testicles, Mc- 

 Clean (1936) investigated the filtrates of CI. welchii, CI. faludis, CI. 

 ovitoxicus, CI. oedematis-maligni, CI. oedematiens and CI. tetani. Of 

 these, the most powerful was that of CI. welchii. He found that 

 0.000,015 ml. of the original toxin filtrate of CI. we^c/iii— equivalent 

 to 0.0014 of the M.L.D. for a mouse— produced immediate diffusion 

 in the dermis, and a sensible increase in an area of diphtheria toxin 

 lesion as compared with the controls. The results with the filtrates of 

 the other organisms appeared to show that the diffusing activity of these 

 filtrates does correspond approximately to the relative local invasiveness 

 of the organisms from which they were obtained. 



The dry weight of the smallest dose of the purified diffusing factor 

 of CI. welchii was 0.000,000,5 mg., or 5X10^"* microgram, which was 

 found to correspond to the activity of the purified testicular extracts. 



The diffusing activity was stated not to be particularly related to 



