290 INFECTION AND IMMUNITY 



The method of obtaining these substances as used both in animal 

 experiments and in the treatment of human subjects is at present as 

 follows : 



Rabbits, preferably of 1,500 grams weight or heavier, receive intra- 

 pleural injections of aleuronat. This is prepared by making a three 

 per cent solution of starch in meat-extract broth, without heating, 

 and adding to this, after the starch has gone into thorough emulsion, 

 five per cent of powdered aleuronat. This is thoroughly mixed, boiled 

 for five minutes, and filled into sterile potato tubes, 20 c.c. into each tube. 

 Final sterilization is done preferably in an autoclave. The rabbit in- 

 jections are carried out by injecting 10 c.c. into each pleural cavity 

 in the intercostal spaces at the level of the end of the sternum, in the 

 anterior axillary line, great care being exerted to avoid puncturing of 

 the lungs. The rabbits are left for twenty-four hours, at the end of 

 which time a copious and very cellular exudate will have accumulated 

 in the pleural cavities. This is removed, after killing the animals with 

 chloroform, by opening the anterior chest wall under rigid precautions 

 of sterility, and pipetting the exudate into sterile centrifuge tubes. 

 Immediate centrifugalization before clotting can take place then per- 

 mits the decanting of the supernatant exudate fluid. To the leuco- 

 cytic sediment is then added about 2 c.c. of sterile distilled water, and 

 the emulsion is thoroughly beaten up with a stiff bent platinum spatula. 

 Smears are now made on slides, stained by Jenner's blood stain, and ex- 

 amined for possible bacterial contamination. It is well also to take 

 cultures. Sterile distilled water is then added to each tube, about twenty 

 volumes to one volume of sediment, and the tubes are set away in the 

 incubator for eight hours. At the end of this time the sterility is again 

 controlled as above, and further extraction in the refrigerator continued 

 until the extract is used. 



In experimenting upon animals, Hiss 1 observed that pneumococcus, 

 staphylococcus, streptococcus, meningococcus, and typhoid, dysentery, 

 and cholera infections in rabbits and guinea-pigs were profoundly modi- 

 fied when injections of leucocyte extracts, prepared as above, were ad- 

 ministered intrapcritoneally or subcutaneously during the course of the 

 infection. In many cases animals were saved by these substances from 

 infections which proved rapidly fatal in untreated control animals, even 

 when the protective injections were made as late as twenty-four hours 

 after intravenous infection, 



1 Hiss, Jour. Med. Res., N. S., xiv, 3, 1908. 



