Probable Value to B. coli of '" Slime" Formation in Soils. 371 



force. The character of pulse curves, taken either with a Hiirthle or other 

 spring manometer, placed in direct communication with an artery, or by 

 means of the sphygmograph, depends very largely on the " lability " of the 

 conducting arteries. It is arterial " lability," not reflection of waves, which 

 modifies the form of the pulse curve taken in different arteries. While the 

 pressure waves produced by the heart may remain the same, the form of 

 the sphygmogram may be altered, and what has been termed a " high " or 

 a "low" pressure curve may be produced by variation in the "lability" of 

 the conducting arteries. The wall of an artery is supported by the 

 surrounding tissues and skin, the whole being permeated with blood ; it will 

 be a matter for further consideration as to how far the lability is affected 

 by the condition of the surrounding tissues. Comparison of figs. 8 and 9 

 shows how large a part the tissues normally take in supporting the arteries. 



On the Probable Value to Bacillus coli of " Slime" Formation in 



Soils. 

 By Cecil Revis. 



(Communicated by Sir J. R. Bradford, K.C.M.G., Sec. E.S. Received April 8, — 



Read April 24, 1913.) 



During the course of an investigation into the causes of variation in the 

 physiological activity of Bacillus coli, a number of experiments were started, 

 in which soils, either virgin or mixed with cow dung or human excreta, were 

 inoculated with cultures of B. coli, together with cultures of various soil 

 organisms so different from the colon organism that they could not be 

 mistaken for it on plating out. The requisite quantity of soil was placed 

 in a layer about f-inch deep in large flat litre-bottles, and the cultures 

 were added in the form of emulsions in physiological salt solution, made 

 from agar slopes. Sufficient water was also added to make the soil 

 visibly moist. The bottles were closed with cotton-wool plugs and kept 

 at ordinary room temperature in the dark. Controls which were inoculated 

 with all the organisms except the B. coli were started at the same time. 

 The soils were examined from time to time by withdrawing about 5 grm. 

 by means of a sterile tube, shaking this up with 50 c.c. of sterile water, 

 spreading plates directly on to ordinary agar and incubating at 20° C. 



It was found very difficult to isolate the B. coli in this way because of the 

 rapid and expansive growth of the other organisms present, and because the 



