THE SYNTHESIS OF PROTEIDS. 153 



ammonium sulphate, or sodium chloride. Here they espe- 

 cially resemble the class of proteids called globulins. 



5. Another resemblance to globulins is seen in their 

 behaviour to a stream of carbonic anhydride, which in the 

 presence of salts causes precipitation. The passage of a 

 current of air through the mixture redissolves the pre- 

 cipitate. 



6. The colloid B is not digested by pepsin-hydrochloric 

 acid ; A is slightly digestible ; but C is easily digested, and 

 then the solution gives the typical peptone colour, pink, on 

 the addition of copper sulphate and caustic potash. 



7. Each of the colloids when intravenously injected into 

 animals (rabbits, cats, dogs, rats, guinea-pigs) causes exten- 

 sive intravascular coagulation. In a typical experiment 

 death is due to respiratory failure, and 5 to 20 c.c. of a 

 1*5 per cent, solution is usually fatal. The other symptoms 

 noticed are pronounced exophthalmos and dilatation of the 

 pupil ; in dogs there is often hyperpncea immediately before 

 death. 



This last property of the proteid-like colloids is the 

 most remarkable of the series, and its discovery is entirely 

 due to Dr. Pickering. The resemblance to the action of 

 the nucleo-proteids is most marked, and extends even to 

 minor points, e.g., neither cause intravascular clotting in the 

 blood of albino rabbits ; and in dogs very minute doses 

 indeed, cause a slowing of the rate of coagulation ; but for 

 these and other details the reader must consult the original 

 papers. 



I need hardly say that the result was an unexpected 

 one, and it by no means lessens the difficulties surrounding 

 the coagulation question. So far as was previously known 

 only nucleo-proteids produced intravenous clotting, with 

 the single exception of snake poison. Snake poison, how- 

 ever, produces extensive disintegration of the vascular wall, 

 and so it was considered that this was the source of the 

 nucleo-proteid. The artificial colloids produce on the other 

 hand little or no disintegration of leucocytes, and no injury 

 to the capillary walls, so that the same explanation will not 

 hold here. 



