﻿4 EESISTANCE OF ANIMALS TO MICRO-OKGANISMS. 



Unexpected difficulties were encountered all along in conducting the 

 investigation. The problem of maintaining an atmosphere of fairly 

 constant composition, with the relative proportions of the impurities 

 ranging within the prescribed limits, was a difficult one to solve, and 

 in fact could not be attained with the apparatus employed. It was 

 deemed advisable to expose the animals to the impure atmosphere for 

 at least a month before inoculating them, consequently it was found 

 impossible to maintain the atmosphere at the desired point of impurity 

 during the entire experiment. At times the impurities fell below the 

 prescribed limit, and, in turn, the air supply fell, especially during 

 the night, to a point below that at which it would support life, and 

 some or all of the animals were smothered, and the experiment had to 

 be started over again. 



In consequence of these difficulties only six experiments have been 

 brought to a conclusion. A number of others were commenced, but 

 failed through the loss of several or all of the animals; these accidents 

 occurring frequently after the animals had been under experiment for 

 several weeks and were nearly ready for the inoculations. Much time 

 was lost in this manner. 



Because of the difficulties encountered, and the indefinite character of 

 the results obtained, only two forms of atmospheric impurities were 

 tested — ^that of the respiratory impurities with animals in bell- jars 

 arranged in series as in the Brown-Sequard experiments, and the effects 

 of ordinary atm^ospheric air containing 0.5 to 2.0 per cent, by volume 

 of pure carbonic acid gas. Each form of experiment was repeated 

 successfully three times, using different micro-organisms for the inocula- 

 tions with each of the three sets of experiments. 



A. Inoculations with staphylococcus pyogenes aureus. 



Experiment I. 



Respiratory impurities. — Six rabbits were placed under bell-jars of 

 37 litres capacity, arranged in series as in the Brown-Sequard experi- 

 ment. A current of air was maintained through the series of bell-jars 

 by means of a water pump. The experiment was commenced May 19, 

 1896, and terminated June 29, 1896. The animals were inoculated on 

 June 23 with 1 cc. of a 24-hour old bouillon culture of staphylococcus 

 pyogenes aureus. The details of the experiment are shown in Table I. 



