CYTOLYSINS 127 



birth the complement content of the blood has been found to be rather 

 small; Gay has found it to be somewhat less in women than in men. 

 Moro has found it to be less in bottle-fed than breast-fed babies. 

 Although individual variation may be great, there is a certain uni- 

 formity in different members of the same species. This is true through- 

 out a large number of species, except the horse, in which species it is 

 found to vary markedly. Different species as such contain different 

 amounts of complement. The guinea-pig contains, as a rule, more 

 complement per cubic centimeter than other species. Man and rabbit 

 contain less than the guinea-pig, and in the case of the mouse it is 

 very difficult to demonstrate any complement at all. It has recently 

 been found that insects and mollusks contain practically no complement. 

 Alterations of Amount of Complement. The amount of comple- 

 ment in a given blood may be made to vary by artificial means. For 

 example, the injection of indifferent materials, such as foreign blood 

 plasma, bouillon, aleuronat, pepton, yeast, nuclein, physiological salt 

 solution, produces an increase in the amount of complement, but this 

 increase is not permanent. Similarly complement may be increased for 

 a short time following the injection of pilocarpin, phlorizin, staphylo- 

 cocci, oil of turpentine and thyreoidin ; exposing an animal to high 

 temperatures may also increase complement. Although it is generally 

 true that complement is not increased by immunization, nevertheless 

 Cantacuzene has recently shown that by injecting red blood-corpuscles 

 into certain marine invertebrates he is able to increase the amount of 

 complement in their blood. Complement may be reduced temporarily 

 by the injection of sodium taurocholate, potassium picrate, toluylendi- 

 amin and more permanently by experimental phosphorus poisoning, 

 experimental chronic suppuration, starvation and by alcohol poisoning. 

 If sensitized blood-cells, i.e., blood-cells saturated with amboceptor, 

 are injected into an animal, it can be demonstrated that the amount of 

 complement is reduced by the hemolysis which takes place in vivo. 

 Shaw has found that in the case of recently acquired syphilis, although 

 the blood before treatment shows no alteration of complementary ac- 

 tivity, yet the administration of salvarsan may reduce this activity 

 to a considerable degree. The experimental investigations of the effect 

 of disease in man on the complement content of his blood are very 

 unsatisfactory because human blood normally contains only a small 

 amount of complement and the detection of any variation is susceptible 

 to a wide margin of experimental error. 



Method of Obtaining Complement. Complement is usually obtained 

 from the guinea-pig-, although under special circumstances it may be obtained 

 from other animals. The blood may be withdrawn in any manner adapted to 

 such a procedure. In the case of the guinea-pig the method employed in this 

 laboratory is to anesthetize the animal very slightly, pull the hair from the 

 neck, make a longitudinal slit in the mid-line of the neck, place a 15 c.c. centri- 

 fuge tube toward the upper end of the slit with its lip firmly pressed into the 

 opening, then with a scissors snip the carotid artery, carefully avoiding the 

 trachea. The animal is then held head downward while the blood drains into 

 the tube. The blood is allowed to clot in the tube and the clot separated from 

 the side of the tube with a long sterile or clean needle, as the necessity of the 

 case indicates. The clot separates best at room temperature, but if centrifuga- 



