October 1, 1886.] 



KNOWLEDGE ♦ 



549 



3. Whale-like 



(Cetacra) 

 i. Hoofed 



Htrax or Rock- 

 Rabbit . 

 {Mi/raooiih'u) 



G. Trunked . 



(Probosciilea) 

 7. Flesh-feedees 



8. 



10. 



11. 



Gnawers . 



(Sodentin) 



Insect-feeders 



(Jnst'ctii'ora') 



Finger-winged 



( Cheiroptera') 



Lemurs 



{Lemitr.iiilea) 



Whales : dolphins; porpoises; also adapta- 

 tion ot structure to aquatic life. 



Very numerous and valuable order. 

 Divided into the odd-toed — as tlie horse, 

 the tapir, and his near relation, the 

 rhinoceros; and the ereii-ioed — as swine 

 and their near relation, the hippo- 

 potamus ; camel ; deer ; sheep ; ox ; all 

 these are plant-feeders. 



Represented by a small animal, the coney 

 of the Bible. The shape of the teeth 

 points to affinities between hoofed 

 animals on the one hand and gnawing 

 animals on the other. 



Represented by the elepliant, tlie longest- 

 lived and most acute of plant-feeders. 



Seals ; bears ; weasels ; wolves and other 

 members of the dog family ; lions and 

 other members of the cat family. 



Hare ; rat ; beaver ; squirrel. A very wide- 

 spread class. 



Mole, hedgehog. 



Bat, highly organised and closely allied to 

 insect-feeders. 



The lemurs are sometimes grouped with 

 monkeys in the order of the " four- 

 banded," a division falling into disu.se ; 

 but they have marked affinities with 

 marsupials, gnawers, and insect-feeders. 

 The " Hying lemur," or colugo, a squirrel- 

 like creature with webbed hands, appears 

 to be an interesting link between insect- 

 feeders and primates. 



Monkeys ; baboons ; man-like apes (gibbon, 

 ourang-outang, chimpanzee, gorilla), big- 

 jawed, small-brained, stooping posture ; 

 Man, big-brained, erect posture — divided 

 into races according to shape of skull, 

 colour of skin, nature of hair. 



Tn the past and pre.sent life- history which has been sum- 

 marised in tliis and foregoing papers, no bi-eak in the con- 

 tinuity of life, or in its fundamental unity, is found. In 

 tlie unstableness of the first living matter lay tlie tendency 

 to that varixtion which, acted upon by manifold agencies in 

 the production of unlikenesses both seen and unseen, lias 

 resulted in ever-increasing complexity of forms. But it is 

 not e;\sj', in the disconnected shape in which these papers 

 are presented, to keep clear and constant before the reader 

 the relationship between all life that is and that has been, as 

 well as the identity of that life with, and its dependence 

 upon, the not-living. Perhaps this interrelation may be 

 made more apparent in the exposition of the theory of 

 evolution wliich is now to follow the description of the 

 things evolved. 



End of Part I. 



12. Primates 



PLEASANT HOURS WITH THE 

 MICROSCOPE. 



By Henry J. Slack, F.G.S., F.R.M.S. 



HE subject of bacteria in connection with 

 health and disease not only continues to 

 occupy the attention and jjerplex the en- 

 deavours of scientific men, but, as articles 

 in the daily papers show^, interests a large 

 circle of readers who are too often supplied 

 with statements wide of the true mark. 

 Anybudy who has a microscope can easily become acquainted 

 with the leading facts and principles of these researches. A 

 few globules of yeast in a little sugar and water in a small 

 cell placed on the stage of the microscope in a warm room 

 will bud (pullulate) and multiply under the eye of the 



observer, and, as every one knows, a rearrangement of the 

 molecules of the sugar occurs, resulting in the giving off of 

 carl)on diox3de (carbonic acid) and the formation of alcohol. 

 All fermentations resemble this one of yeast. They are 

 resiilts of a ferment which is a minute plant feeding itself 

 at the expense of the substance fermented, and causing the 

 molecules it does not want for its own subsi.stence to anange 

 themselves in new patterns. When beer turns sour little 

 ferments have acted upon the alcohol and made vinegar ; 

 when butter turus rancid a ferment has been the cause; and 

 when a bit of meat putrefies other ferments have combined 

 to pull the whole complicated structure to pieces, and all 

 except tiie mineral constituents are dispersed in the gaseous 

 state. 



The products of fermentation may be whole.some, as in the 

 case of leavened bread, or may be highly injurious ; and when 

 a physiologist is endeavouring to trace out the cause of an 

 infectious or contagious disorder, he must distinguish be- 

 tween the operation of the microferments themselves and 

 that of the new combinations to which they give rise. If a 

 man gets drunk upon fermenting beer no one accuses the 

 little yeast plants of ujisetting his equilibrium, because the 

 specific action of alcohol quite free from yeast is well known. 

 In numerous cases of what are called zymotic diseases the 

 exact chemical change produced by the ferments is not 

 known, and it requires great skill and many trials to find 

 out what the ferments alone can do in the way of injuring 

 healthy animals into whose system they are introduced. 



One difficulty occure at the ver}' threshold of the inrpiiry. 

 Many little ferments are so commonly and widely dis- 

 seminated that it needs great care to keep them out. For 

 example, brewers frequentlj- have large quantities of beer 

 spoilt because, besides the yeast ferments which tliey want, 

 othei's get in which induce a fresh or destructive fermenta- 

 tion immediately after the j'east plants have caused the 

 right one. Wine-makers are exposed to similar losses, as it 

 frequently happens that they cannot exclude the mischief- 

 makers. In that case Pasteur counselled destroying them 

 by boiling. This saves the wine in a drinkable state, but 

 it will no longer improve by keeping and acquire those 

 aromatic properties known as its hoiiqiiet. 



Many of the disease ferments are difficult to discern with 

 the highest powei's, partly from their extreme smallness, 

 and partly from their being of nearly the same refractive 

 power as the fluid in which they are immersed. To make 

 plain this question of refraction to those who liave not studied 

 optics, let the difference be noticed between the visibility of a 

 piece of glass immei'sed in clear water, and the impossi- 

 bility of recognising a spoonful of water poured into a 

 tumbler of water of the same temperature. A drop of 

 alcohol is distinguishable from water into which it is thrown 

 until it gradually mingles with that fluid and is lost in it. 

 Sometimes a micro-ferment, like the bacterium of tubercular 

 diseases (consumption, ifcc), can be made visible by staining 

 with an aniline or other dye. Ferments that are easily 

 seen, and others much more easily not seen, may be in the 

 same fluid, and it has often happened that some experimenter 

 has ascribed to the things he saw the work done by those 

 he did not see, and whose existence he did not suspect. 

 Let us suppose an experimenter has contrived to obtain a 

 pure specimen of fluid containing a .specific micro-ferment; 

 his troubles may then begin. To get it in a position 

 ready for the microscope he puts a drop on a glass slide, 

 which ought to be perfectly clean, and not to hold any 

 object that could be mistaken for a micro-ferment. Any 

 ordinary jierson would be offended if told they could not 

 clean a piece of glass, but making anything perfectly clean 

 is a task requiring considerable manipvilative skill. A 

 piece of glass may be washed with strong acid, capable of 



