56 



THE COMPOSITION OF EXPIRED AIR, 



the air of the laboratory, developed in the cultures. In the other instances the cultures remained 

 sterile. The fluid used in these cultures was taken from the portions remaining after the animals 

 were inoculated. This fact, in all probability, accounts for the contaminations noted. There is no 

 evidence that any micro-organisms were carried over in the exhaled breath while collecting the 

 fluids for the inoculations. The nature of the organisms which developed in these cultures indicates 

 that they gained entrance to it while the fluid was being warmed and inoculated into the animals. 



VII. — Experiments causing animals to breathe air recently expired by other animals. 



These exiieriments are designated as " 15rown-Sequard " experiments. The apjjaratus used 

 consists of a series of bell jars, four to six in number, connected together by means of glass and 

 rubber tubing, and so arranged that a continuous current of air is conducted through the entire 

 series. The apparatus is shown in Fig. 8. The first animal receives pure air only, the second 



Fig. 8. — Brown-Sequard apparatus. 



animal receives the air coming from the bell jar containing the first animal, the third that coming 

 from the second, while the last animal receives air that has traversed the entire series, and, conse- 

 quently, contains the impurities added to it in its course through all the other jars. 



THE " BROWN-SIiQUARI) " APP.^R.^TUS — FIG. 8. 



The Nos. I, 2, 5, 6 represent four of the six bell jars in the series. 



a, represents the gas meter. 



b, represents a small P>lenmeyer flask containing about too c. c. of water. The bubbles pro- 

 duced by the air passing through the water show whether aspiration is regular or not. 



r, represents a Woulff bottle attached between the Erlenmeyer flask and pump to prevent the 

 entrance of water into the apparatus when there is negative pressure in the apparatus. 



d, re])resents the water tap. 



e, represents a Chapman water pump, which creates the suction and maintains the ventilation. 

 The glass and rubber tubing connecting the different parts of the apparatus, as shown in the 



figure, has an internal diameter of nine mm., while that used to connect the seven-litre bell jars 

 was only five mm. in its internal diameter. 



DKSCRIPTION OK THF, " HROWN-SI5qU.\RD " APP.\RATUS — FIG. 8. 



The bell jnrs rest on large ground-glass plates, and, in order to produce an air-tight joint, the 

 base of the bell jar is well rubbed with beef suet (well adapted for this purpose). In addition to 

 this, the joint is sealed with melted paraflfinc. If this work is carefully done there is no possibility 

 of leakage at these joints. The bell jars are connected together by means of glass tubing bent at 

 right angles and mserted through a perforated rubber cork fitted into the openings near the top and 

 bottom of the jar. The air enters the apparatus through the gas-metre. The metre is connected 

 with the first jar by means of rubber tubing attached to the glass tube inserted into the upper 

 opening of this jar. After passing through this jar it takes its exit by means of the glass tube 

 inserted into the lower opening, and connected with a similar glass lube inserted into the upper 

 opening of the second jar by means of a short piece of rubber tubing. It takes the same course 

 through all the jars. 



The bell jars shown in the figure represent those used for the rabbits, and have a capacity of 

 37,ooo c. c. A wooden box, four inches in depth and just large enough to allow the bell jar to be 



