2QO HANDBOOK OF PHYSIOLOGY. 



taken to his method of investigation. Firstly, because his tambour ar- 

 rangement does not admit of both positive and negative pressure being 

 simultaneously recorded. Secondly, because the method is only applicable 

 to large animals, such as the horse. And thirdly, because the intraven- 

 tricular changes of pressure are communicated to the recording tambour 

 by a long elastic column of air; and fourthly, because the tambour ar- 

 rangement has a tendency to record inertia vibrations. H. D. Rolleston, 

 who has pointed out the above imperfections of Marey's method, has re- 

 investigated the subject with a more suitable apparatus. The method 



Fig. 169. Tracings of (1), Intra -auricular, and (2), Intra- ventricular pressures, and (3), of the im- 

 pulse of the heart, to be read from lefr to right, obtained by Chauveau and Marey's apparatus. 



adopted by Eolleston is as follows: a window is made in the chest of 

 an anaesthetized and curarized animal, and an appropriately curved glass 

 canula introduced through an opening in the auricular appendix. 

 The canula is then passed through the auriculo-ventricular orifice with- 

 out causing any appreciable regurgitation, into the auricle, or it may be 

 introduced into the cavity of the right or left ventricle by an opening 

 made in the apex of the heart. In some experiments the trocar is 

 pushed through the chest wall into the ventricular cavity. The appa- 

 ratus is filled with a solution of leech extract in .75 per cent saline so- 

 lution, or with a solution of sodium bicarbonate of specific gravity 1083. 

 The animals employed were chiefly dogs. The movement of the column 

 of blood is communicated to the writing lever by means of a vulcanite 

 piston which moves with little friction in a brass tube connected with 

 the glass canula by means of a short connecting tube. 



When the lower part of the tube (A) is placed in communication with 

 one of the cavities of the heart, the movements of the piston are re- 

 corded by means of the lever (c). Attached to the lever is a section of 

 a pulley (H), the axis of which coincides with that of the steel ribbon 

 (E); while, firmly fixed to the piston, is the curved steel piston rod (1), 



