190 



THE POPULAR EDUCATOR. 



extent i.e., when it is used to stand for all the objects which it 

 can signify; and undistributed, if used only for a part of them. 

 Hence, from what has been said above, it will appear plain that 

 the subject is distributed in all universal propositions, but never 

 in singulars. In other words, the quantity of the proposition 

 determines the distribution of the subject. The distribution, 

 however, of the predicate depends upon a different considera- 

 tion. This is regulated not by the quantity but by the quality of 

 the proposition. A little reflection will make this clear. When 

 we say " all are men mortal," what we are really doing is this 

 we are speaking of all the objects signified by the term " man," 

 and affirming of them that they are mortal i.e., that they 

 belong to the class of mortal objects. But in so doing we are 

 not dealing at all with the rest of the class of mortal beings 

 besides man e.g., birds and beasts ; we are leaving them out of 

 consideration altogether, and the proposition would be equally 

 true whether or not there were any other mortal beings besides 

 men. In other words, we are using the term mortal, the predi- 

 cate of the proposition, in an undistributed sense ; and this 

 takes place in every affirmative proposition, whether universal 

 or particular. In negatives, however, the case is otherwise. 

 Let us take as an example, "no vice is useful." Here we are 

 really speaking of the whole class of objects to which the term 

 "useful " is applicable, and denying that " vice " can be found 

 amongst any of them, that any part of the predicate agrees 

 with the subject. Hence the predicate is always distributed in 

 a negative proposition, for the simple reason that if any part of 

 that for which the predicate stands were to agree with the sub- 

 ject, and not disagree with it, the proposition would not be true. 

 The result may be thus summed up. (1.) All universals (and 

 no particulars) distribute the subject. (2.) All negatives (and 

 no affirmatives) distribute the predicate. 



With reference to their quantity and quality, taken together, 

 logicians are accustomed to denote every proposition by one of 

 the four first vowels of the alphabet, as a symbol to represent it. 

 Thus: ~ ; 



Symbol. Propositio?i. 



A Universal Affirmative, 



E Universal Negative, 



I Particular Affirmative, 



O Particular Negative, 



Example. 



" Every man is an animal.' 

 " No man is a stone." 

 " Some man is just." 

 " Some man is not just." 



Having thus given some account of the most important 

 classifications of propositions, it will be more convenient to say 

 a few words upon another subject (which could not, perhaps, 

 have been so readily understood at an earlier period), before 

 proceeding to consider the different relations which propositions 

 bear to one another. 



We have already explained what is signified by universal 

 terms ; but the reader must also learn that these have, from the 

 time of the earliest treatises upon Logic, been divided into 

 five classes, called predicables, termed respectively " genus," 

 " species,"'" difference," "property," and "accident." 



A genus may be described as a universal term which contains 

 under its signification that of two or more other universal terms. 

 In this way " animal " is to be regarded as a genus, as compre- 

 hending under the idea for which it stands the ideas represented 

 by the other universal terms " man," " beast," " bird," etc. 



A species-is a universal term which is contained under another 

 more universal term e.g., " man " is a species of the genus 

 "animal," as forming a part of what it comprehends. 



It is to be noticed that the same term may often be regarded 

 as genus or species, according as it is considered with reference 

 to the terms which it contains, or those under which it is con- 

 tained. Thus " man " is a species of the more universal term 

 "animal," but a genus when regarded as containing under it 

 the less universal terms or species "negro," "white man," 

 ' European," "American," etc. A genus which is so compre- 

 hensive as to be contained under no other is called the highest 

 genus; and a species which, on the other hand, contains no 

 species under it, but merely comprises individuals, is called the 

 lowest species. All between these are known by the names 

 of sub-alternate genera or species. 



A difference is the name given to the attribute which distin- 

 guishes a particular species from all the other species which are 

 included under the same genus. Thus, "rational" is the dif- 

 ference which distinguishes the species "man" from the other 

 species included under the genus "animal." And if we define 



man" as a "rational animal," we have what is called a 

 logical definition i.e., one made up of the genus and essential 

 difference. 



A property is the name of an attribute found in all lie indi- 

 viduals of a species, and which, though not of the essence of the 

 species, is necessarily joined to it e.g., " being influenced by 

 motives" is a property of "man," necessarily following from 

 his being "rational." 



An accident is an attribute which, though not necessarily joined 

 to the difference, is yet found in some of the individuals of the 

 species. It may be inseparable i.e., found in all the individuals 

 of the species, though not necessary to their existence as such 

 e.g., "blackness" in crows; or separable i.e., not universally 

 found in the species i.e., not amongst all the individuals or not 

 in the sam r individuals at all times e.g., "blackness" or 

 " sleeping " in men." 



In our next lesson we shall proceed with the consideration of 

 the relations which the different kinds of propositions bear to 

 one another. 



HUMAN PHYSIOLOGY. III. 



THE MUSCULAB SYSTEM. 



THE external fleshy covering of the skeleton is composed of a 

 large number of separate portions, called muscles. A muscle is 

 formed of the aggregation of a number of small bundles of 

 reddish fibres, which, in their turn, are bound together by fibrous 

 tissue. There are two great varieties of muscular structure in 

 the body the muscles of animal life, or voluntary muscles, 

 which are the muscles proper ; and the muscles of organic life, 

 or involuntary muscles. The structural distinction between tho 

 two classes is that the fibres of tho first, when examined under 

 the microscope, present a number of fine dark parallel markings, 

 but the fibres of the involuntary muscles present no such ap- 

 pearance. The latter derive their name from the fact that they 

 are concerned in the performance of the functions of organic 

 life, and act independently of the will ; they form tho muscular 

 walls of the digestive canal, of the windpipe and its divisions, 

 of the ducts of glands, of the blood-vessels, and of some other 

 parts ; they also enter largely into the composition of the skin, 

 causing by their contraction that peculiar sensation called 

 goose-skin. There are other muscles which should be included 

 in this class, if we consider their functions and independence of 

 mental control such is the heart, which is a hollow muscle, 

 composed of the striped fibres of the voluntary class, but acting 

 entirely independent of the will, and performing one of the chief 

 functions of organic life. The division is, indeed, rather an 

 arbitrary one, as the voluntary muscles constantly perform 

 involuntary actions, and the involuntary ones are frequently 

 affected by the will or other acts of the mind. The chief cha- 

 racteristic property of muscles is their elasticity and power of 

 contraction, either by direction of the will or the application of 

 a stimulus. During the process the muscle appears to swell up, 

 becoming rounder and harder ; the bulk of the muscle is not 

 increased, but its fibres are shortened and become more tense. 

 By the act of contraction a considerable amount of heat is 

 evolved, whether from chemical action or mechanical friction of 

 the fibres is uncertain ; in this we find an explanation of the 

 origin of part, at least, of the increase of temperature that is 

 produced by active exercise. The voluntary muscles are the 

 organs of locomotion ; and if we consider the manifold and 

 diverse movements of which the body is capable, we shall be 

 prepared to find them very numerous ; they exceed four hundred 

 in number, and vary much in form and size. As a rule, they ara 

 thick in the centre, which is free, and end in thinner tendons, 

 composed of white fibrous tissue, where they are connected 

 with the bones. In the neighbourhood of some of the joints, anc? 

 where a muscle passes over a prominence of bone, and by its 

 action would be likely to cause an injurious amount of friction, 

 little membranous bags containing fluid, and called bursas 

 (French bourse, a purse), are interposed ; these enable the muscle 

 to glide more easily over the opposing surface. 



There are two principles upon which the muscles may be 

 arranged for consideration namely, location and action. Thus 

 we might describe the muscles of tho face, the ear, or the eye. 

 On the other hand, we might speak of the muscles of mastication, 

 respiration, or articulation ; a combination of the two will be 

 most adapted to show the general actions of the muscles, and 



