September 22, 1922] 



SCIENCE 



325 



To see that a marked change may be pro- 

 duced by modifying the colloidal state of the 

 protective substance, a slide was made with a 

 solution containing egg albumen as the colloid. 

 The solution was then heated until the albumen 

 began to show a milkiness, another slide was 

 made, and after drying was compared with the 

 fii-st unhealed specimen. The difference in 

 crystallization is considerable. 



Unusual crystalline forms such as sphero- 

 crystals and sheaf-like groups which are so 

 often seen in the crystals of substances derived 

 from organisms, are very often consequent 

 upon the protective action of some colloid from 

 which they are not entirely purified. Another 

 curious occurrence must be mentioned here, 

 which may be termed auto-protection because 

 it is due to iso-eolloidiam. Before reaching 

 the ordinary visibly crystalline state, particles 

 of every substance must pass through the col- 

 loidal zone, and the particles first reaching that 

 state may interfere with the normal crystalliza- 

 tion of the rest. Thus ammonium salts, even 

 without the addition of protective colloids, are 

 prone to assume feathery or fern-like forms. 

 The phenomenon is marked in the oleates and 

 is probably the underlying cause of the forma- 

 tion of myelins, although their formation is 

 fostered by such lipoid protectors as eholestrin. 

 According to J. G. Adami (Harvey Society 

 Lecture, 1906), if certain simple soaps be dis- 

 solved 'by warming on a slide with water and 

 then allowed to cool, they may show upon 

 examination in the polarizing microscope a 

 perfect rain of doubly refracting spherules, 

 which, . depending on the nature of the soap, 

 may last for hours or days or else immediately 

 give place to a brilliant white layer of formed 

 crystalline plates. The fluid crystals of 0. 

 Lehmann are probably examples of auto-pro- 

 tection, and W. B. Hardy, E. Hatsehek and 

 others have described substances which form 

 unstable gels that soon become crystalline. 



An indication that the colloidal state is 

 anomalous is given by the fact that, while the 

 sun attracts microscopic particles, and even 

 crystalloidally dispersed particles, it selectively 

 repels colloidally dispersed particles, as in the 

 tails of comets (See J. Alexander, "Colloid 

 Chemistry" ) . 



The bio-colloids are so readily aifeeted by 

 salts, H-ion concentration (effective reaction), 

 temperature, actinic (sun's rays) and traumatic 

 (shaking, mechanical injury) effects, that it is 

 more sui-prising that plants and animals 

 should breed true, than that they should show 

 variations. Therefore, although individuals 

 may be much affected by such changes during 

 their lives, it is evidently a rare occurrence 

 that these changes are registered in the germ 

 plasm by which alone they may be transmitted 

 to offspring. The specificity of the germ plasm 

 is evidently guarded by many factors, among 

 which seem to be selective adsorption and dif- 

 ferential diffusion of dissolved substances 

 through its protecting walls or membranes. 

 Nevertheless unusual influences must occasion- 

 ally change it materially without destroying it, 

 and along this line experiment may be directed. 

 It may be that the germ plasm can be affeoted 

 through the somatoplasm, as well as by direct 

 means. And of all the variations, in natui-e 

 only the beneficial changes survive. 



With highly developed organisms the com- 

 plications are enonnous. We are jusit begin- 

 ning to realize the importance of enzymes, 

 hormones, internal secretions (endocrines), 

 essential "impurities" like the vitamines, 

 iodine and manganese, and the necessity of a 

 suffl'cient variety of food to include enough of 

 each of the essemtial amino-aeids, outside of 

 mere fat-carbohydrate-protein-calorie figures. 

 Therefore, even if experiments with higher 

 forms of life may yield more numerous results, 

 it may be better to begin with the simpler 

 forms where the results may be more readily 

 traced to their causes. Nor must it be imagined 

 that this will prove an easy matter; for filter- 

 able bacteria, invisible in the ordinary micro- 

 scope and not resolvable by the ultra-miero- 

 seope if visible in it, whose size is of the order 

 of some of the protein molecules, are still capa- 

 ble of breeding true. 



Consideraition should be especially given to 

 conditions that are apt to be met with in nature 

 or which may have existed in geologic times. 

 The effect of small quantities of substances 

 such as manganese in plants and iodine in 

 mammals should not be overlooked. Even 

 strong acidity or alkalinity may be produced 



