102 



kind of diminution, viz. that which takes place in 

 natural respiration, that we are at present concern- 

 ed ; and as this cannot be determined by experi- 

 ments made on brutes, we must resort to the facts 

 which have been ascertained by those instituted on 

 the respiration of man. 



85. A knowledge, however, of the diminution of 

 bulk which the air, during respiration, suffers, im- 

 plies a previous determination of the quantity ordi- 

 narily inspired. To ascertain this point, many modes 

 of experiment have been adopted, and the conclu- 

 sions which have been drawn from them very widely 

 differ. Borelli estimated the bulk of air taken in at 

 a single inspiration, at 15 cubic inches * ; Mr Kite 

 from 12 to 17 t ; Dr Goodwyn at 14 { ; Mr Davy 

 from 13 to 17 ; and Drs Jurin, Hales, Haller and 

 Sauvages, at 4O cubic inches. With the conclusion 

 of these latter authors the experiments of Dr Men- 

 zies nearly coincide, and as the methods which he 

 adopted seem less liable to objection than those of 

 any other author, it may not be improper shortly to 

 give the detail of them. He procured an allantoid, 

 and fixed to it a machine consisting of two pretty 

 large tubes, joined at right angles, nearly in the 

 form of a common brass cock. One end of the 

 horizontal tube was connected with the allantoid, 

 and the other received into the mouth, while the 

 upright tube, which rose from its centre, communi- 



* De Motu Animal. 



j- Essay on Apparent Death, p. 24. 



J Connexion of Life with Respiration, p 28. et seq. 



Researches, p. 410. & 433. 



