166 



tractions of death. The latter always contain more red particles in 

 their substance than those of cold blood, and are sooner deprived of 

 their irritability, 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, &c. 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 a 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 

 human 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 

 affected 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. 



Experiments for ascertaining how far Telescopes will enable us to 

 determine very small Angles, and to distinguish the real from the 

 spurious Diameters of celestial and terrestrial Objects: with an 

 Application of the Result of these Experiments to a Series of Ob- 

 servations on the Nature and Magnitude of Mr. Harding's lately dis- 

 covered Star. By William Herschel, LL.D. F.R.S. Read De- 

 cember 6, 1804. [Phil. Trans. 1805, p. 31.] 



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 



