178 BIOLOGY AND TECHNIQUE 



For the isolation of dysentery bacilli from feces, no satisfactory 

 special methods have as yet been devised. Here we can depend only up- 

 on careful plating upon agar and gelatin and extended colony " fishing," 

 and the study of pure cultures. The complete absence of motility of 

 these bacteria is of much aid in such identification. 



The determination of tubercle bacilli in stools is difficult and of 

 questionable significance, in that they may be present in people suffer- 

 ing from pulmonary tuberculosis as a consequence of swallowing sputum 

 or infected food, and in that there may be other acid-fast bacilli, such 

 as the timothy bacillus, present. 



Blood Cultures. — The diagnosis of septicemia can be positively made 

 during life only by the isolation of bacteria from the blood. Such exam- 

 inations are of much value and are usually successful if the technique 

 is properly carried out. A large number of methods are recommended, 

 the writers giving, however, only the one which they have found 

 successful and simple for general use. 



The blood is taken by preference from the median basilic vein of the 

 arm. If, for some reason (both forearms having been used for saline 

 infusion), these veins are unavailable, blood may be taken from the 

 internal saphenous vein as it turns over the internal malleolus of the 

 ankle joint. The skin over the vein should be prepared, preferably an 

 hour before the specimen is taken, with green soap, alcohol, and bichlo- 

 rid of mercury, as for a surgical operation. The syringe which is used 

 should be of some sterilizable variety (the most convenient the Luer 

 model), which is easily manipulated and does not draw with a jerky, 

 irregular motion. Its capacity should be at least 10 c.c. It may be 

 sterilized by boiling for half an hour, or preferably, when all-glass syringes 

 are used, they may be inserted into potato-tubes and sterihzed at high 

 temperature in the hot-air chamber. Before drawing the blood, a linen 

 bandage is wound tightly about the upper arm of the patient in order to 

 cause the veins to stand out prominently. When the veins are plainly 

 in view, the needle may be plunged through the skin into the vein in a 

 direction parallel to the vessel and in the direction of the blood-stream. 

 After perforation of the skin, while the needle is groping for the vem, 

 gentle suction may be exerted with the piston. Great care should be ex- 

 ercised, however, that the piston is not allowed to slip back, and air be, 

 by accident, forced into the vessel. In most cases no suction is necessary, 

 the pressure of the blood being sufficient to push up the piston. After the 

 blood has been drawn, it should be immediately transferred to the proper 

 media. Epstein has recently recommended the mixture of the blood 



