Physiology : A manual for students and practioners / by Theodore C. Guenther and Augustus E. Guenther.

  • Guenther, Theodore C. (Theodore Charles)
Date:
1903
Catalogue details

Licence: Public Domain Mark

Credit: Physiology : A manual for students and practioners / by Theodore C. Guenther and Augustus E. Guenther. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    2. That roprodiK'tioM prcvciit.s variation ami preserves the uiii- f'orinity ot tlie racv. .'{. That by iVt'sh coinbinatioii.s it Lfives rise to variations. The living matter of the fertilized ovum is acted upon by two forces—heredity, wliich preserves its characteristics, and athiptn- tioii, which changes tliem. Heredity includes the transmission of both actual and jniteiiiial characteristics from [nirents to oH'spring. The resemblance is most complete between child and parent, and tiiminishes directly backward along the ancestral line. The re- send)lances may be inKitmnica/, j>lnj,siol()(/lca/, or jtxijelto/tjtjica/, or all three variously combined and related. Characters that d(j not appear in the jjarent, but are transmitted from grandparent to child, are called latent and give rise to atavimn or neersioit. Tkia occurs mod often when two strains are crossed; thus half-castes are usually more degraded than either their civilized or savarje parent. The inheritance of (ic^n/rer/ rharacter.'< is a problem that has not yet been solved. It cannot be denied to exist in unicellular oriranisms, where the protoplasm of the parent becomes directly that of the offspring. In the human being, cases of transmissal of acquired characters can be explained otherwise. However, germinal infections of syphilis can take place through the ovum or spermatozoon. Intra-uterine infections of typhoid, scarlatina, endocarditis, small-pox, measles, croui)()Us pneumonia, and anthrax have been okserved to take place, but these are not comparable to a modification of the germ-plasm through heredity in the ordi- nary sense. The basis of heredity lies undoulitedly in the substance of the germ-cells. Home biologiists maintain that the chromatic is the sole germinal substance. Others regard both protoplasm and nuclear matter as essential, since the characteristics of every cell depend upon its metabolism, and this in turn depends upon the integrity of protoplasm and nuclear matter. Whatever the basis is, it may be designated as rjmn-jidisni. The origin of germ-plasm is ex])lained by two views: 1. It may arise from small particles, r/cnuuuli's ('' lift/r (/rrm-':''), given off from the various cells of the body ami collected into germ-cells. 2. It may not be formed in the body, but bi- siinplv transmitted from generation to generation, an<l be directly continuous from one