Jan. 10, 1883.] 



KNOWLEDGE ♦ 



39 



"Star Atlas," by the Editor of Knowledge, we might have 

 extended our list almost indefinitely. Even as it is, we 

 may be permitted to e.xpress a hope that we have not 

 wholly failed in our attempt to indicate what a mine of in- 

 struction and delight lies before the possessor of even so 

 small an instrument as that to which our descriptions ha^■e 

 had reference. We have said nothing of what may be 

 observed in the Moon, or the Sun, or of the planets Mercury 

 and Venus. 



Fii.'. O'.i. 



Fi!r. 70. 



••• 



Cephei. 



Cq.!.. 



Cc.,.l,. 



In the case of lunar observation alone, a very large 

 amount of work of the most interesting possible character 

 may be accomplished by the aid of a three-inch telescope, 

 and should uny considerable number of our brother readers 

 feel sufficient interest in selenography to desire it, we shall 

 be willing to give such directions and details in papers 

 supplementary to this, as may enable them to commence 

 and follow the study of the Moon's surface to the greatest 

 advantage. A single paper might, if rciiuired, suffice to 

 deal with the Sun and (what we may call) the two daylight 

 planets. Finally, in connection with the stellar portion of 

 our subject, we may say here, that should any possessor of 

 a three-inch telescope desire to verify what he may have 

 heard or read with reference to spectrum analysis, as 

 applied to these distant suns we have been examining, 

 McClean's Star Spectroscope is the only one at all applicable 

 to such an instrument as that whose employment we have 

 presupposed. With that exceedingly ingenious little 

 instrument the spectra of such stars as Sirius, Vega, 

 Aldebaran, and Orionis, and other bright ones, may be 

 very well seen indeed, even in a three-inch telescope. 



OUR BODIES: 



SHORT PAPERS ON PHYSIOLOGY. 



By Dr. Andrew Wilson, F.RS.E. 



Xo. IT.— LIFE AND WORK. 



IF there is any word in the English language which may 

 be considered well-nigh synonymous with, or equivalent 

 to, " life," it is the word " change." At least, I can find 

 no otlier term which, within the compass of a single word, 

 expresses so succinctly the great characteristic of living 

 beings. Life itself, whether viewed from a general, or from 

 a microscopic and more intimate standpoint, is a scries of 

 changes, prevailing throughout the body that lives, and 

 working out in the daily and hourly existence of the frame. 

 Physiolog}- is the "Science of Finiclions," and the business 

 of the physiologist, briefly stated, is merely that of 

 chronicling and explaining the changes through which the 

 living body passes in the course of its history. TiCt us 

 briefly regard these changes in the tirst instance, by way of 

 gaining a clear notion of the general course of the events 

 which constitute the " life " so-called, equally of man and 

 the monad. 



It may appear to be a paradoxical statement, and yet it 



is one involving the gravest truth, that a human body at 

 any given moment is not precisely the same in respect of 

 its weight, substance, and composition, as at the preceding 

 moment, or at the subsequent one. At no moment of 

 existence do the changes — chemical and physical — of which 

 our bodies are the continual theatre, cease. This fact is 

 susceptible of convincing proof. If we weigh a man before 

 he performs an hour or two of hard work, and then weigh 

 him again after the performance of his task, we shall find 

 him to be appreciably lighter. He has lost suV)stance 

 through the actions involved in doing the work ; and phy- 

 siology is able to trace where that substance has gone. With 

 every breath the man gave out, so much of his substance 

 disappeared in the form of (1) carbonic acid (/as; (2) 

 iralcr ; (3) /teal; (4) other waste matters (ammonia, 

 mva, etc.) ; whilst we may add that he has been evolving 

 and exerting a greater or less amount of inechanical force, 

 or in plain language vork. In truth, the waste matters 

 which a living body is constantly emitting, and the loss of 

 substance the body undergoes, is the result of the irork it 

 performs. There is the closest parallel to be drawn between 

 a living body in this respect and a steam-engine. The 

 latter works, and as the result of its work exhibits wear 

 and tear. If the work is great, the waste will be propor- 

 tionately great. And so with the body. Work, there, 

 means waste, as in the machine, and like the machine, the 

 living being wastes in proportion to the work it performs. 



It is quite evident, however, that the changes we have 

 described are, in themselves, far more complicated than 

 might at first sight be supposed. The living body is the 

 seat of changes and actions of intricate chemical nature. 

 For instance, we know that without /leat the bodily pro- 

 cesses — or, what is much the same thing, life itself — would 

 cease. How is heat produced in a living body 1 The 

 answer is, much in the same way that heat is evolved 

 in a fire. The o.ri/r/cti gas contained in the air 

 we breathe, unites with certain materials — carbon 

 and htjdrorjen — contained in the blood. The result 

 of this combination is the production of heat ; 

 whilst water and carbonic acid gas are also given 

 ofT, and form the literal " ashes " of the bodily fire. Thus 

 constant chemical change produces the heat necessary for 

 life's continuance, and it can be proved that the quantity 

 of carbon and hydrogen uniting with oxygen within the 

 body in a known period, will account for the heat which is 

 evolved during that period of time. As also illustrating 

 the chemical changes which the living body undergoes, we 

 may cite the intricate actions connected with the digestion 

 of food in the mouth, stomach, and intestine. Our very 

 existence in its plainest phases, is, in truth, maintained 

 through the constant operation of a chemistry, which, 

 though it may be called " vital," is in reality one with the 

 chemical operations which we see taking place in nature 

 around us. 



The constant nature of the changes which occur in a 

 living body has already been insisted upon. There is no 

 cessation from their action ; or, to put it in another way, 

 we experience no cessation of work. Our bodily substance 

 is constantly being used up in the acts of living. Suppose 

 we ofTer to support a man only so long as he does some 

 work or other, we might deem our part of the bargain null 

 and void if he slept or rested. But the idle man, as daily 

 experience proves, must eat and drink, as does the busy 

 individual. The idle hieing might justifiably enough hold 

 us to our part of the contract, by proving to us 

 what physiology declares to be sober truth, namely, 

 that even during idleness or sleep, the body works. 

 The heart never ceases its work ; the lungs and the 

 breathing muscles apparently know no cessation from 



