KNOWLEDGE ♦ 



fjAX. 5, 18^3 



and swimming vigorously with a spiral motion. Thoy are, 

 in fact, screw-jiropclifrs, and as the; lower forms of life are 

 very ancient, their ancestors, no doul)t, practised that mode 

 of propulsion millions of years Ueforc it was imitated Viy 

 man. After a little while, longer threads will Ijo found, 

 and probably some branching like the mycelium of the 

 moulds. Most of the disease-germs identified by various 

 observers are, more or less, like the smallest of the 

 little rods discernible with a ([uarter-inch objective. 



The use of experimentingwitli a varietyof infusions is two- 

 fold : first, there is a chance of getting a variety of germs ; 

 and, second ly,diirerent substances favour the development of 

 dill'erent kinds of infusorial creatures. Whenever a sunbeam 

 lights up a swarm of motes, there is sure to be amongst 

 them minute eggs and germs of small plants, animals, and 

 objects that lie on the border-land. Professor Tyndall 

 throws artificial sunbeams of electric light through air in 

 glass vessels, and while motes are visible, life will appear, 

 if the germs amongst them are allowed to settle in fluids 

 that will feed them. When there are no motes, a fluid 

 capable of putrescence, but in which all germs have been 

 destroyed by heat, will remain sweet in the purified air for 

 any length of time. Country air on breezy heaths and 

 downs is comparatively free from motes and germs, and on 

 lonely mountains, in calm weather, none are found. As 

 it is most important in thickly-peopled countries to secure 

 breathing-places that are not contaminated, the greatest 

 care should be taken to stop the robbery of open land by 

 adjacent proprietors. Sandy beaches and chalk downs, for 

 example, are invaluable as sanitoriums and playgrounds, 

 and for enabling winds to send pure air to cities. Pasteur 

 has distinguished small, round bodies producing silkworm 

 disease ; little rods producing splenic sheep disease ; others 

 generating chicken cholera, which is common on French 

 farms ; and lately he has identified an organism which can 

 produce rabies in dogs, and which appears to be the source 

 of the poison conveyed in the bite of mad animals. 



In the Department of Eure-et-Loire !^-"),000 animals 

 ■were inoculated upon Pasteur's plan in 188:!. In the last 

 few weeks 13,000 sheep, 3, .500 oxen, and 20 horses were 

 similarly treated without a single accident. 



M. Paul Bert has recently injected the blood of a mad 

 dog into a healthy one without communicating the disease. 

 He finds the poisonous microbe to reside not in the secre- 

 tion of the salivary glands, but in the mucus of the 

 mouth and air passages. 



It may be said of these organisms generally that they 

 are capable of growing under different conditions, and 

 sometimes they can be developed under various forms 

 which might be taken to belong to different species. The 

 malignant disease germs can, in certain known cases, and 

 probably in others, either be cultivated so as to preserve 

 their evil power for successive generations, or by supplying 

 them with free oxygen, so that their descendants are less 

 and less poisonous and finally harmless. Inoculation with 

 the milder forms protects against the action of the more 

 virulent. The moulds that will grow in some of the 

 bottles are related to the useful ferments and also to those 

 ■which produce disease. 



In the Xciccaslle Wcrk/,/ Chronicle for Saturday, the 

 6th inst, will appear the first of a series of weekly columns 

 on popular science, by Mr. Proctor. 



Thk lulitor of KNowLEDfJE will lecture on the Star- 

 Depths, at St. tJeorge's Hall, Langhara-place, on Sunday 

 afternoon, at four o'clock. The lecture will be illustrated 

 ■with the o.vyhydrogen light. 



OUR BODIES: 



SHORT PAPERS ON PHYSIOLOGY. 



Bv Dk. Andrew Wilson, F.R.S.E. 



No. III.— MUSCLES. 



ON one occasion I asked a class of students who were 

 studying physiology in a popular fashion, what they 

 supposed " muscles " were. The answers I received to my 

 incjuiry were more distinguished for their variety than for 

 their correctness. One student said " muscle " was " sinew" ; 

 another told me it was " some kind of fibre " ; a third said 

 it was "gristle " ; and a fourth that it was " some kind of 

 pulp found in the bod}'." Now the students in question 

 were drawn from the ranks of ordinary middle-class 

 society. They were studying physiology with me, not 

 as a matter of business, but as a labour of love, and 

 were attempting, under my guidance, to obtain a broad 

 and general view of the functions and structure of the 

 human frame. (We should bear in mind that physiology 

 is the science of " functions," and that, as such, it is based 

 on a knowledge of "structure.' ) I may therefore take my 

 former students as a type of intelligent society around us, 

 and I am not far wrong, I fancy, when I add that if I were 

 to ask the readers of Kxowledce, head overhead, to return 

 me a plain answer to the question " What is muscle '! " I 

 should find only a very small percentage of correct replies. 

 Yet in the appreciation of what muscle is, to begin with> 

 lies the key to the understanding of the whole topic. 

 Muscle, in one word is j/es/i. Our muscles are our "flesh," 

 as the muscles of any other animal are its "flesh." What 

 we eat of fish is the muscle of the animal, or rather the 

 collective muscles. Our mutton-chop is the " muscle " of 

 the sheep, as veal is ox muscle in a young condition. 



We should never despise homely sources of information. 

 The homelier such means of knowledge are, the better. 

 Here, then, is a readily-accessible source of information 

 concerning the nature of muscle. A slice of cold roast 

 beef lies before me. With the point of my fork I can 

 make out that it consists of things that look to the un- 

 assisted sight like coarse ji/jrts, but which are really 

 bundles of fibres. This is observation number one. Muscle 

 is made up of fibres, or bundles of fibres, joined together. 

 Next, I can see that in my slice of beef (which represents 

 a cross cut of muscle) there is to be perceived a line of 

 division, through which I can separate so much of the beef 

 from the other half, without tearing any of the fibres. 

 Now this second observation shows me that the flesh of the 

 body is not all in one mass. On the other hand, if I were 

 to examine a whole leg of beef I should find that the flesh 

 thereof was grouped into separate portions, each of which 

 is a muscle. With the handle of a dissecting scalpel, we 

 can separate out each muscle as a rule from its fellows, 

 and we see that freedom of movement for each muscle is 

 thus secured. 



At this stage of our inquiries, we might ask ourselves 

 ■what, generally, are the uses of muscles. I can enume- 

 rate at least five functions which are performed by 

 muscles. Firstly, there are the coituiwn movements of the 

 body : walking, grasping, itc. These are performed by 

 muscles. Secondly, we obviously sjiea/c by muscular aid. 

 Thirdly, ■we express our emotions — from sneezing and 

 snarling with our raised lip and uncovered tooth, to 

 shrugging our shoulders — by means of muscles. Fourthly, 

 we circulate our blood by muscular action, for the heart is 

 simply a hollow muscle. And fifthly, muscle Itelps in tin' 

 dhjestion of food, for the middle coat of the stomach and 

 intestine, not to speak of the gullet, is muscidar, and serves 



