Coexistence with Prccipitable Substances 129 



hand, Michaelis and Oppenhcimer note that immunified animals present 

 a different appearance if examined two to three days after an injection. 

 Here solid masses of albumin are found, either free or attached to the 

 peritoneal surface, the masses, when viewed in section, showing an 

 outer zone, due to leucocytic infiltration (chiefly microphages, with 

 macrophages at periphery). The parietal and intestinal peritoneum 

 is covered by small tubercle-like nodules made up of nests of leucocytes'. 

 Intravenous injections, they found, produced a leucocytosis, due almost 

 exclusively to mono-nuclear elements, the leucocytosis being more marked 

 in immunified animals. 



Considerable interest attaches to the observation that a precipitin 

 and precipitable substance may coexist in the serum of immunified 

 animals. It was purely by accident that Mr Hopkins (Reader in 

 Physiological Chemistry, Cambridge) and I had occasion to observe 

 this in 1901, in connection with rabbits which had been treated with 

 crystallized horse albumin, and I herewith append the protocol of the 

 experiment. 



Three rabbits bled 29, vir. 1901. 



Treatment : Intraperitoneal injection of crystallized horse albumin. First in- 

 jection 22, vi., last 20, vn. 1901, all bled nine days after last injection. Total amount 

 injected 50, 50 and 53 c.c. of solution (strength undetermined) respectively, in graded 

 doses of 5 c.c., rising to 10 c.c. for last three injections, the day intervals between 

 injections being 5, 4, 5, 5, 9. The weights of the rabbits were (in g.): 



At 1st injection At last injection When killed 



I. 1690 1750 1580 



II. 1940 1980 1600 



III. 1910 1780 1520 



Rabbit I. bled from the car vein four days after injection 5, showed presence 

 of precipitin for the solution with which treatment had been administered. 



It is noticeable that the weights of all the animals had fallen very 

 considerably during the days preceding death, this being somewhat 

 unusual and the reason not clear. The animals were bled to death and 

 their sera collected in the usual way. When we came to test their 

 precipitating power, we found Sera I. and III. to give a large precipita- 

 tion, whereas Serum II. gave no reaction at all. Before this fact 

 was discovered, in order that a test en gros might be made, Serum II. 



1 The authors found that injection of albumoses, either subcutaneously or iutraperi- 

 toneally, only produced sterile abscesses at the point of inoculation, or strong peritoneal 

 adhesions. See further on the effects of bipod injections in Metchnikoff, VlmmuniU, 

 Paris, 1901. 



v, 9 



