. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. 14 PHYSIOLOGY OF THE DOMESTIC ANIMALS. are concerned, cannot be distinguished from the contents of all active forms of cells (Fig. 2). The amoeba is capable of spontaneous motion, both as regards change of external form and of progressing from place to place. Motions may also be evoked by various stimuli; hence, free protoplasm, in common with muscular fibre and ciliated organisms, is contractile. The peculiarity of protoplasmic motion, as seen
. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. 14 PHYSIOLOGY OF THE DOMESTIC ANIMALS. are concerned, cannot be distinguished from the contents of all active forms of cells (Fig. 2). The amoeba is capable of spontaneous motion, both as regards change of external form and of progressing from place to place. Motions may also be evoked by various stimuli; hence, free protoplasm, in common with muscular fibre and ciliated organisms, is contractile. The peculiarity of protoplasmic motion, as seen in the amoeba, is that motion does not occur around a fixed point, but rather is a flowing motion, such as might occur in the particles of a fluid. Thus, in an amoeba the changes in form and location are effected through the thrust- ing out of lobe-like prolongations of the periphery (pseudopodia), and their subsequent withdrawal or the flowing into these extensions of the remainder of the body. Occasionally one or more of these pseudopodia become gradually more and more constricted, until, finally, a portion becomes entirely separated from the original mass, increases in size, and itself possesses all the proper- ties of the parent stock; hence, protoplasm is reproductive, and possesses the power of growth. Moreover, the move- ments of an amceba are not necessarily the consequences of external stimuli, but may be self-originating; hence, protoplasm is also automatic. If watched for some time, an amceba will often be seen to take into its interior, by flowing around them, small vegetable organisms, of which portions are dissolved and converted into the substance of its body, while the undigested remainder is extruded ; therefore, protoplasm, even in the absence of all digestive organs, possesses the power of nutrition. The amoeba requires for its existence an atmosphere of oxygen, which is absorbed, and which it again partly exhales as carbon dioxide. Protoplasm is therefore r
Size: 2356px × 1061px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiol, bookyear1890
