Page:Proceedings of the Royal Society of London Vol 1.djvu/186

Rh tractions of death. The latter always contain more red particles in their substance than those of cold blood, and are sooner deprived of their initability, even though their relative temperature be preserved. It appears, also, that respiration in the former tribe is more essential to life than in the latter.

Various experiments are next mentioned on the substances which accelerate the cessation of irritability in muscles when applied to their naked ﬁbrils, such as all narcotic vegetables, poisons, muriate of soda, the bile of animals, 8m. Discharges of electricity, passed through muscles, destroy their irritability, but leave them apparently inﬂated with small bubbles of gas, owing, perhaps, to some combi- nation which decomposes water. Workmen who are exposed to the contact of white lead, nitric acid, or quicksilver, frequently expe- rience local spasms or partial palsy. _

Lastly, some arguments are adduced which prove that} smaller quantity of blood ﬂows through a muscle in the state of contraction than during its quiescent state; that when muscles are vigorously contracted, their sensibility to pain is nearly destroyed; and that the hliman muscles are susceptible of considerable changes, from extra- ordinary impressions on the mind, such as grief, fear, uncommon attention, mental derangement, &c. ; in all which cases uncommon muscular exertions have been observed, which could not have been aﬁ'ected without the operation of those stimulants.

Sect. 6.—This section contains some conclusive remarks, chieﬂy on the effects of stimuli on the muscles, as they are distinguished into voluntary, involuntary, and mixed. For the classiﬁcation. of these agents here stated, we must refer the curious physiologist to the paper itself; having already, perhaps, trespassed too far upon the time that can well be spared for the abstract of this lecture.

Dr. Herschel commences his paper by stating, that, being desirous of ascertaining the magnitude of the moving celestial body lately dis- covered by Mr. Harding. and intending, for that purpose, to make use of a ten-feet reﬂector, it appeared to him a desideratum highly worthy of investigation, to determine how small a diameter of an object might be seen with that instrument. He had. he says, in April 1774, determined a similar question relating to the natural eye ; and found that a square area could not be distinguished from an equal circular one till the diameter of the latter came to subtend an angle of 2' 17" ; but, as he did not think it right to apply the same conclusions to a telescopic view of an object, he, in order to