262 PART V.-WORKING STAGE. 



respiration." (Ibid., p. 125.) Or note how minute observation 

 revealed that without the presence of infinitesimal portions of 

 several classes of as yet unidentified vitamines, an otherwise 

 perfect diet, consisting of pure proteins, carbohydrates, fats, 

 and mineral salts, fails to sustain health and life, and that an 

 addition to such a diet of 2 cc. of milk daily, sufficed to restore 

 the balance; or remember the shock the layman felt when he 

 heard (1894) that argon, a constituent of the air far from in- 

 significant in quantity, had escaped the notice of earlier chemists, 

 and his gratification at learning that helium, neon, krypton, 

 and xenon, which were found to exist in the atmosphere, are 

 present there in the proportion of one part in 245,300, 80,800, 

 20,000,000, and 170,000,000 parts by volume respectively. 



We offer here two detailed instances where minuteness of 

 observation is strikingly evidenced: 



Edwin S. Goodrich, in the Evolution of Living Organisms, 1912, thus 

 describes the process of indirect cell division or karyokinesis : "The 

 chromatin gathers together into a coiled thread, the linin network becomes 

 disposed as a system of fibres radiating through the cytoplasm from two 

 minute bodies, the centrosomes. Between these centrosomes the fibres 

 join across, forming a spindle. The centrosomes can be seen to originate 

 from the nucleus or its neighbourhood, as a single body which divides, 

 the two halves moving to the opposite sides of the nucleus. The chro- 

 matic thread now breaks up into a definite number of separate pieces, 

 the chromosomes, which arrange themselves in a circle round the equator 

 of the spindle. Each chromosome now divides into two halves which 

 travel to the opposite ends of the spindle. There they join together to 

 form a thread; the thread breaks up into granules; the system of fibres 

 disappears; and thus a new nucleus is reconstituted, similar to the resting 

 nucleus of the original cell. A division of the cell-body then yields two 

 nucleated cells. As a rule the centrosome persists to give rise to that of 

 the next division. Now it is important to notice the continuity of sub- 

 stance during this process of division. Cytoplasm, linin, centrosome, and 

 chromatin are all parcelled out to the two daughter cells; above all, each 

 daughter nucleus receives the same number of chromosomes, and apparently 

 exactly the same amount of chromatin." (P. 22.) 



The nature of the "internal secretions" produced by certain diminutive 

 glands, regarded until recently as of no importance, has provided one of 

 me most fascinating chapters in physiology. "The chemical substances 

 contained in the internal secretions have been named hormones, or ex- 

 citants, by Bayliss and Starling. In certain cases the chemists have been 

 able to isolate these hormones, and in one case the chemical constitution 

 is known and the substance has been manufactured artificially in the 

 laboratory. In other cases, and these the majority, they are as yet only 

 known by their definite stimulating action. Quite recently it has been 

 shown that bodies similar in nature to the hormones must be present in 

 our daily diet, or certain typical nutritional diseases are produced. These 

 hormones are not foods in the sense of being necessary to provide energy 

 by their combustion; they are only required in minute amounts as ex- 

 citants, and in their absence certain very specific effects giving the clinical 

 symptoms of well-known diseases appear. In a liberal and mixed diet all 

 the necessary hormones required from outside are contained. But, when 

 the diet is very restricted, such as the rice diet used by the Indian coolie, 

 unless the thin brownish layer surrounding the inner white part of the 

 rice be eaten in the daily diet, a disease with marked nervous lesions 

 appears, called beri-beri. This disease long puzzled medical scientists, 

 but it is now clearly shown to be caused by the absence from the diet 



