THREE:It might have been expected that, on reaching physiology, the Stagirite would stand on firmer ground than any of his contemporaries. Such, however, is not the case. As already observed, his achievements belong entirely to the dominion of anatomy and descriptive zoology. The whole internal economy of the animal body is, according to him, designed for the purpose of creating and moderating the vital heat;315 and in apportioning their functions to the different organs he is entirely dominated by this fundamental error. It was a common notion among the Greeks, suggested by sufficiently obvious considerations, that the brain is the seat of the psychic activities. These, however, Aristotle transports to the heart, which, in his system, not only propels the blood through the body, but is also the source of heat, the common centre where the different special sensations meet to be compared, and the organ of imagination and of passion. The sole function of the brain is to cool down the blooda purpose which the lungs also subserve. Some persons believe that air is a kind of food, and is inhaled in order to feed the internal fire; but their theory would involve the absurd consequence that all animals breathe, for all have some heat. Anaxagoras and Diogenes did, indeed, make that assertion, and the latter even went so far as to say that fish breathe with their gills, absorbing the air held in solution by the water passed through thema misapprehension, says Aristotle, which arose from not having studied the final cause of respiration.201 His physiological theory of generation is equally unfortunate. In accordance with his metaphysical system, hereafter to be explained, he distinguishes two elements in the reproductive process, of which one, that contributed by the male, is exclusively formative; and the other, that contributed by the female, exclusively material. The prevalent opinion was evidently, what we know now to be true, that each parent has both a formative and a material share in the composition of the embryo. Again, Aristotle, strangely enough, regards the generative element in both sexes as an unappropriated portion of the animals nutriment, the last and most refined product of digestion, and therefore not a portion of the parental system at all; while other biologists, anticipating Mr. Darwins theory of pangenesis in a very wonderful manner, taught that the semen is a con316flux of molecules derived from every part of the body, and thus strove to account for the hereditary transmission of individual peculiarities to offspring.202
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THREE:The expense of patterns should be divided among and charged to the machines for which the patterns are employed, but there can be no constant rules for assessing or dividing this cost. A pattern may be employed but once, or it may be used for years; it is continually liable to be superseded by changes and improvements that cannot be predicted beforehand; and in preparing patterns, the question continually arises of how much ought to be expended on thema matter that should be determined between the engineer and the pattern-maker, but is generally left to the pattern-maker alone, for the reason that but few mechanical engineers understand pattern-making so well as to dictate plans of construction.
THREE:(1.) What does the term "machinery of transmission" include, as applied in common use?(2.) Why cannot direct comparisons be made between shafts, belts, and gearing?(3.) Define the relation between speed and strain in machinery of transmission.(4.) What are the principal conditions which limit the speed of shafts?In the shadows Hetty listened to as much of the talk as she could hear. But nobody was going to leave the house without her knowledge. Behind the hangings in the hall she waited. Her patience was not unduly tried. There was a light footstep presently, a pause as if of precaution, and the Countess came downstairs. Her hair had become blonde, there was a lace shawl over her head, her skirts were short and trim.
