The principles of physiology / by John Gray McKendrick.

  • John Gray McKendrick
Date:
[1912]
Catalogue details

Licence: Public Domain Mark

Credit: The principles of physiology / by John Gray McKendrick. Source: Wellcome Collection.

    29/272 (page 25)
    existence, the typical form is nearly spherical, as seen in the ovum, and also in many of the minute cells of which the body is composed. Living matter never assumes crystalline forms; it does not grow like a crystal, by the deposition of new matter on its surfaces, but by absorbing matter into its substance and usually trans¬ forming this into matter like itself. A crystal does not transform, and it grows by the deposition of new layers on its surface; living matter can transform, or assimilate, and it can grow by the transformed matter becoming part of its substance. It is re¬ markable, however, that dead matter may assume forms very similar to the forms of living matter. In certain media crystallisable substances may take on organic shapes, and various mixtures of soaps, gums, etc., may form a froth which, under the microscope, may show forms very similar to that seen in living stuff. In some circumstances even the move¬ ments of living matter may be imitated. Thus, a highly complex substance called protagon can be extracted from yolk of egg by hot alcohol. If a minute portion be