PHYSICAL AnD LITERARY. 44 
but, fometimes, after expiration is finifhed, 
a panfe of 15, 20, 30, or more feconds will 
intervene, before a new in{piration is begun. 
Much the fame thing happens to. animals 
who have fwallowed too great a quantity of 
opium *, 
Now, if it be reafonable to afcribe the flow, 
deep and interrupted breathing, in fuch 
cafes, to the infenfibility which attends thofe 
difeafes of the head; and which ofzum never 
fails to produce, when taken too liberally ; 
are we not hence led to conclude, the lefs re- 
markable change of breathing which hap- 
pens in fleep, to be owing, partly, to the 
fenfe of feeling in the lungs, being then 
fomewhat diminifhed, tho’ in a much lefs 
degree than in thofe morbid cafes? 
To conclude with fumming up what has 
been faid in a few words; in ordinary fleep 
the fenfibility of the heart and lungs fuffer 
fo fmall a diminution, that their motions 
will be very little more affected by it, than 
they would be from the horizontal pofition 
_and reft of the body, and compofure of mind 
attending it. In the deeper fleep, which 
fucceeds great fatigue, the motions of the 
heart 
* Effay on the Vital and Involuntary motions, &c. p. 194. 
