112 C. C. WARDEN, J. T. CONNELL AND L. E. HOLLY 



A notable feature of the results was the irregularity in kilhng 

 time. Not infrequently a toxic broth which killed one guinea- 

 pig in two days did not kill the other of the pair until much 

 later. We attempted to account for this pecuhar result by 

 recognizing the extreme instabihty of such colloids, the sHghtly 

 different conditions encountered in the tissues of the various 

 guinea-pigs sufficing to alter the physical state of the injected 

 fluid. 



Control guinea-pigs that died following injection of Strepto- 

 coccus and of Pneumococcus artificial antigen broth showed 

 puhnonary congestion and hemorrhages without particular 

 damage to kidneys or adrenals. 



The most serviceable colloids of mastic were found, after 

 many trials, to be those prepared by adding to an alcohohc 

 solution of mastic of known concentration the desired amount 

 of alcohohc solution of fat antigen, and then emulsifying in 

 sterile water or salt solution by adding the alcoholic mixture to 

 the fluid kept in constant whirling motion. The emulsions were 

 pale white with orange colors by reflected fight, and the par- 

 ticles were beyond the limits of microscopic vision. The clearest 

 results were obtained with colloids containing 5 mgm. of mastic 

 and 5 to 8 mgm. of the K salt antigen in 100 cc. of diluent, and 

 brought to a pH of 7.9-8.0 with NaOH. On standing the pH 

 shifts to the acid side. The injections were made with freshly 

 prepared sterile emulsions. 



The pathological picture exhibited in guinea-pigs dying from 

 diphtheria and artificial toxin, while characteristic, presents 

 certam features which in the long run do not appear to be dis- 

 tinctive of that poison alone. Out of the control animals in 

 number at least equal to the determinants and kept under the 

 same conditions, there were found two pigs dead following 

 injections of supposedly tuberculous urine showing hemorrhages 

 into the adrenals, and one apparently normal pig, without 

 infection, showing the same lesion. The kidneys of these ani- 

 mals were not noticeably affected. These three control guinea- 

 pigs were the only examples however, in this and in previous 

 work upon fat antigens, in which lesions in any way similar to 

 those of diphtheria toxin were observed. 



