Experimental morphology / by Charles Benedict Davenport.

  • Charles Benedict Davenport
Date:
1897-1899
Catalogue details

Licence: Public Domain Mark

Credit: Experimental morphology / by Charles Benedict Davenport. Source: Wellcome Collection.

    293/302 (page 275)
    attacks a different constituent of the protoplasm. In this way the dissimilar substances in protoplasm are made strikingly apparent. Not only does the protoplasm of one cell show this differentiation, but that of different cells of the body stains very diversely. Another line of evidence for the complexity of pro- toplasm is gained from the study of the effect of poisons. We have seen that the same poisonous substance acts very differently upon allied species of organisms (e.g. of bacteria) and upon the various organs of the body, — a fact which in many cases can only be accounted for on the ground of dissimilar composition. Again, most protoplasm must contain substances which are acted upon specifically by the different agents ; for instance, certain highly explosive compounds which are set off by contact, certain others which are disturbed by light, and still others which are especially changed by heat. Each compound, again, must form an inconsiderable part of the whole, for (if the action be not too intense or prolonged) the “stimulus” of the agent results in no disturbance of the activities in general. Likewise, the facts of acclimatization, according to which, ap- parently, certain substances in the protoplasm may be destroyed without other important change in activities, give additional insight into protoplasmic complexity. Finally, the same agent acts in varying degree on closely related protoplasm, and this indicates that, even when the general composition is the same, the proportions of the different substances vary. From the facts of protoplasmic staining and of the varied effects of poi- sons, from the diverse effects of other stimulating agents, and from the facts of acclimatization of organisms, we conclude that in dealing with protoplasm we are not always dealing with the same thing, but, on the contrary, with very diverse combi- nations, which have this in common, that they exhibit life. § 2. The Limiting Conditions of Metabolism Metabolism is life. To know the limits within which it can occur is to know the vital limits. It is impossible to define these limits closely, however, for, at either extreme, metabolism graduates insensibly into inaction. It will be necessary, conse- quently, to place our limits very far out.