• 328 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



relation of inspiration to expiration, best noted by causing 

 them to register themselves on a revolving cylinder. Various 

 . means of doing this have been suggested by different autliors. 

 One of the simplest consists of a needle pushed into the dia- 

 phragm, and connected by a thread with one of Marey's levers 

 (see I, Fig. 143). Marey's pneumograph consists of a cylinder 



Fig. 113.— Methods of Eegi&tering "R op! ration. 



A is the levor of Marey's registering apparatus; B is a hollow drum, with 

 open tube below, and covered at the top with a piece of thin caoutchouc, on 

 which rests a tin plate connected with the lever A. When the air is blown 

 into B, the caoutchouc is lifted, and the lever rises. "When air is drawn out, 

 the caoutchouc sinks, and the lever falls. The tube of b may be connected 

 by india-rubber tubing with the respiratory passages in several ways, c is a 

 T-tube, open at one end and connected at the other with a cannula (d), which 

 is placed in the trachea of the animal and brought into communication by its 

 upright limb with B. Instead of D, an india-rubber catheter may be placed in 

 the animal's nostril, e is a caoutchouc bag, which is tied over the animal's 

 muzzle and used instead of the tracheal cannula, f is a large vessel, from 

 ■which two tubes (g and h) proceerl. G is connected with the lever b, and it 

 with the respiratory passages of the animal. I is a needle, which is simply 

 connected with the lever by a thread : when pushed into the diaphragm, it 

 registers the respirations. 



of soft india-rubber, enclosing a spiral spring, whose extremities 

 are connected with two pieces of metal which form the ends 

 of the cylinder. A band is passed round the thorax of the 

 animal, and attached to the ends of the cylinder. The interior 

 of the cylinder is brought into communication vv^ith one of 



