Collected Papers, Tom 6The Laboratory, 1921 |
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Strona 4
... described . In order to eliminate this factor , a series of experiments in which the limb bud was grafted on some other part of the body was undertaken . Here the proper nervous connections did not become established , func- tional ...
... described . In order to eliminate this factor , a series of experiments in which the limb bud was grafted on some other part of the body was undertaken . Here the proper nervous connections did not become established , func- tional ...
Strona 6
... described above , care being taken in lifting it from its bed to take all of the mesoderm pos- sible . It is then transferred on the point of the scissors to the first embryo and fitted into the wound . The orientation of the bud is ...
... described above , care being taken in lifting it from its bed to take all of the mesoderm pos- sible . It is then transferred on the point of the scissors to the first embryo and fitted into the wound . The orientation of the bud is ...
Strona 7
... described above . In doing this it is well to avoid injury to the pronephric duct ( p . 15 ) . Three different factors regarding the placement of the limbs have been considered in these experiments , viz .: 1 ) location of the graft in ...
... described above . In doing this it is well to avoid injury to the pronephric duct ( p . 15 ) . Three different factors regarding the placement of the limbs have been considered in these experiments , viz .: 1 ) location of the graft in ...
Strona 10
... described in the section dealing with this group . Both here and in the superposition experiments all possible positions with regard to the placement of the graft within the limitations stated above were experimented with . Relations of ...
... described in the section dealing with this group . Both here and in the superposition experiments all possible positions with regard to the placement of the graft within the limitations stated above were experimented with . Relations of ...
Strona 26
... described in the previous section . In the eight cases in which reduplications occurrred , the early stages of development were like the normal ( figs . 28 and 29 ) , the reduplicating buds not being noted until at least twelve days ...
... described in the previous section . In the eight cases in which reduplications occurrred , the early stages of development were like the normal ( figs . 28 and 29 ) , the reduplicating buds not being noted until at least twelve days ...
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acrosome Anat anatomy animals anteriorly appendages April asymmetry aurelia axial axis body bud to left calkinsi cavity centrosome chromosomes clot component cones conjugation connective tissue cytoplasm days after operation differentiation digits disharmonic Dorsal view dorsodorsal dorsoventral double ectoderm embryo exconjugant experiments fibers figure function gills glomerulus graft granules ground substance harmonic heteropleural heterotopic HISTORY OF BIOLOGY homopleural idiochromosomes inverted Jour kidney larvae later left limb left side light melanophores mesoderm micronuclei nebenkern normal limb notochord nucleus Operated limb organ orientation original Paramecium physiology pigment plants points portion position posterior present pronephros reduplicating reduplicating bud reduplicating member regeneration region retina reversed right limb bud rods rotation rudiment sections segments single limbs situs inversus species Specimen preserved spermatid spermatocyte spermatogonia stage stain structure swim bladder syncytium tion Transplanted bud transplanted limb tubules visual cells wound Zoöl
Popularne fragmenty
Strona 272 - One has but to study his splendid series of illustrations to realize how animal development was placed upon a plane so advanced that for over a century it was unappreciated. One conclusion of Malpighi, however, was seized upon by contemporary biologists. Apparently, unbeknown to him, some of the eggs which he studied were slightly incubated so that he thought traces of the future organism are preformed in the egg. This error, coupled, for example, with Swammerdam's observation of the fact that parts...
Strona 280 - As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.
Strona 278 - Fifthly, from their first rudiment, or primordium, to the termination of their lives, all animals undergo perpetual transformations; which are in part produced by their own exertions in consequence of their desires and aversions, of their pleasures and their pains, or of irritations, or of associations; and many of these acquired forms or propensities are transmitted to their posterity.
Strona 259 - I frequently and seriously bethought me and long revolved in my mind, what might be the quantity of blood which was transmitted, in how short a time its passage might be effected, and the like.
Strona 254 - But any one who is practically acquainted with scientific work is aware that those who refuse to go beyond fact, rarely get as far as fact ; and any one who has studied the history of science knows that almost every great step therein has been made by the
Strona 254 - It is a favorite popular delusion that the scientific inquirer is under a sort of moral obligation to abstain from going beyond that generalization of observed facts which is absurdly called Baconian induction.
Strona 280 - ... the transmutation of species in itself disproved by the best physiological reasonings, but the additional assumptions which are requisite, to enable its advocates to apply it to the explanation of the geological and other phenomena of the earth, are altogether gratuitous and fantastical. Such is the judgment to which we are led by the examination of the discussions which have taken place on this subject. Yet in certain speculations, occasioned by the discovery of the Sivatherium, a new fossil...
Strona 182 - Average for 8 yrs. 634 1.74 reorganization of the cell (endomixis) without the cooperation of two animals involving syncaryon formation (amphimixis) as in conjugation. After endomixis was worked out, it seemed unnecessary to continue longer the main pedigreed culture and accordingly on May 1, 1915, at the 5071st generation, the experiment was formally considered as closed. The record of divisions for each year of the life of the culture to May 1, 1915, may be tabulated as shown in the preceding table....
Strona 260 - It seems not improbable, but that by these helps the subtilty of the composition of Bodies, the structure of their parts, the various texture of their matter, the instruments and manner of their inward motions, and all the other possible appearances of things, may come to be more fully discovered...
Strona 259 - ... from the arteries into the veins, and so return to the right side of the heart; I began to think whether there might not be a MOTION, AS IT WERE, IN A CIRCLE. Now this I afterwards found to be true; and I finally saw that the blood, forced by the action of the left ventricle into the arteries, was distributed to the body at large, and its several parts, in the same manner as it is sent through the lungs, impelled by the right ventricle into the pulmonary artery, and that it then passed through...