Human physiology : prepared with special reference to students of medicine / by Joseph Howard Raymond.

  • Raymond, Joseph H. (Joseph Howard), 1845-1915
Date:
1901
Catalogue details

Licence: Public Domain Mark

Credit: Human physiology : prepared with special reference to students of medicine / by Joseph Howard Raymond. 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.

    29/712 (page 25)
    iilatod and its life destroyed. Acids and strong alkalies have the power of destroying the movement altogether, while chloroform inhil)its it ti'mporarily. This property of responding to a stinndiis is known as irrit(ibi/ifi/,i\ud the fact that a stimulns a])plied to (»ne part of a mass of protoplasm will produce results in other and distant parts demonstrates the presence of co)idactlviti/. Nutrition.—Another property possessed by living protoplasm is that of nutrition ; by which is meant the power to absorb mate- rial, to convert it into protoplasm, and to get rid of such waste products as have served their purpose or are formed as a result of the activity of the protoplasm. Tliat portion of the process which is concerned iu the building up of the protoplasm is assimilation or anaboUsm, while that concerned with its breaking down or destruction is dis(i'^situi/afio)i or katabolism. A fourth property of protoplasm is that of reprodudion, which will be treated of under the heading Division of Cells. Nucleus.—Eml)edded in the protoplasm is a vesicle of various shapes—spherical, oval, or irregular—which is to be regarded as of great importance, especially in the process of cell-subdivision by which new cells are formed and growth thus brought about. It consists of an external enveloping membrane, the nuclear membrane, enclosing the chromoplasm or intranuclear network, a material resembling spongioplasm, and in the interstices of this is the nuclear matrix. In addition to these there are micleoli, some of which are thickenings of the network like the knots in the spongioplasm, and are called pseudonucleoli, while others are free, the latter being the nucleoli proper, or the true nucleoli. A single true nucleolus is usually found, although this is not always the case. Chromatin and Achromatin.—AVhen cells are stained with hema- toxylin the nuclear membrane, the chromoplasm, and the nucleoli take up the staining-fluid readily, while the nuclear matrix does not; hence the former are said to be made up of chromatin, or to be chromatic ; while the latter is achromatin, or is said to be achro- matic. Other dyes, such as safranin, methyl-green, and carmine, produce the same effect. Chromatin is but another name for nuclein, which is the principal constituent of the nucleus. It is closely allied to the proteids, but is characterized by containing a consideral)le percentage of phosphorus; some analyses give as much as 8 per cent. Nuclein is a compound of nucleic acid with proteids, and it is to the affinity of this acid for the coloring- matter that the staining of chromatin is due. It is more correct to speak of nucleins rather than of a single substance, as the compo- sition of nuclein is not always the same. For a further discussion of this subject the reader is referred to the chapter dealing with Proteids. Centrosome.—As already stated, this is probably to be regarded