VOL. II.] PHILOSOPHICAL TRANSACTIONS. ]Q5 



lay still as before, his eyes being all the time very quick, and his heart beating 

 very regularly : But upon ceasing this blast, and suffering the lungs to fall and 

 lie still, the dog would immediately fall into dying convulsive fits; but he as 

 soon revived again by the renewing the fulness of his lungs with the constant 

 blast of fresh air. 



Towards the latter end of this experiment a piece of the lungs was cut quite 

 off; where it was observable that the blood did freely circulate and pass through 

 the lungs, not only when the lungs were kept thus constantly extended, but 

 also when they were suffered to subside and lie still. Which seem to be argu- 

 ments, that as the bare motion of the lungs without fresh air contributes no- 

 thing to the life of the animal, he being found to survive as well when they were 

 not moved as when they were ; so it was not the subsiding or movelessness of 

 the lungs that was the immediate cause of death, or the stopping the circula- 

 tion of the blood through the lungs, but the want of a sufficient supply of fresh 

 air. 



I shall shortly further try whether the suffering the blood to circulate 

 through a vessel, so as it may be openly exposed to the fresh air, will not suffice 

 for the life of an animal ; and make some other experiments, which I hope will 

 thoroughly discover the genuine use of respiration ; and afterwards consider of 

 what benefit this may be to mankind.* 



Description of Mr. Gascoigne s Micrometer .-^ By Mr. Hook. 



iV^ 29, p. 541. 



In pi. 6, the fig. 1, 2, 3, represent the several parts of this instrument; 

 fig. 4, part of the telescope with the instrument applied to it, and 5 the rest 

 on which the whole is supported. 



Fig. 1 represents the brass box with the whole instrument, except only the 

 moveable cover, and the screws by which it is fixed to the telescope. In this 

 fig. aaaa, is a small oblong brass box, serving both to contain the screws, and 

 their sockets or female screws, and also to cause all the several moveable parts 

 of the instrument to move very true, smooth, and in a simple direct motion. 

 To one end is screwed on a round plate of brass, hhb h, about three inches over; 

 the extreme limb of its outside being divided into 100 equal parts, and num- 



* The fact established by this experiment is of the utmost importance in physiology and the 

 practice of physic, viz, that the mere mechanical action of tlie lungs is not sufficient for the support 

 of life ; which ceases unless these organs (the lungs) be duly supplied Wiih. fresh air. On a know- 

 ledge of this fact is founded the treatment of apparent deatli in new-born infants and in drowned 

 persons. 



t This instrument was before mentioned in No. 25, p. 1^1. 



B B 2 



