ELEMENTS OF STRUCTURE. 



75 



body, and what to the nucleus, as in the case of the hepatic and con- 

 tractile fibre-cells. 



If, as would appear from all this, our knowledge of the composition of 

 the cell is very unsatisfactory from a qualitative point of view, how 

 much more so when we glance at it from the quantitative side of 

 chemistry ! In fact, we are unable to give the quantitative analysis of 

 any single form of cell in the body. 



49. 



In regard to phenomena of vitality observed in cells, they would 

 appear, in the first place, to be of the vegetative type consisting in 

 processes of absorption of matter, transformation and execretion of the 

 same, growth and proliferation. Again, the vitality of the cell is mani- 

 fested in the most striking manner by the extraordinary phenomena of 

 contractility which have recently been met with among the corpuscular 

 elements of the animal body. 



Contractile cells have long been known one might say as curiosi- 

 ties in the bodies of lower animals. Comparatively recently they ha\e 

 been recognised also as existing very widely distributed among the 

 same, and some animals are known of such simple structure that almost 

 the whole mass of the body consists of them. But we have also 

 gradually become acquainted with an ever-increasing number of the same 

 kind of cells in the bodies of the higher animals, likewise endowed with 

 the power of vital contractility. Besides this, such a property could no 

 longer be doubted after the recognition of the fact that a widely-spread 

 species of muscular tissue, known as unstriped, as also the heart (at 

 least at an earlier period of embryonic life), had Consisted of such cells 

 entirely. Taking with all this the fact that, up to the present, this 

 vital contractility has been observed in the cells of all but a few tissues, 

 such as, for instance, those of the nervous system, we are almost war- 

 ranted in concluding that, at an earlier period of their existence,, all 

 cells are endowed with this power of contraction; that is to say, as long 

 as they consist of protoplasm alone, 

 and before they are enclosed in a 

 distinct cell-membrane, and that this 

 power is dependent probably on some 

 property inherent in the latter sub- 

 stance. 



Let us take a somewhat nearer 

 glance at this wonderful phenomenon 

 of cell-life in individual cases. 



If we take a frog in whose eye 

 inflammation has been produced by 

 the action of nitrate of silver applied 

 to the cornea, we find after a few 

 days that the aqueous humour be- 

 comes milky. A drop of this fluid, 

 placed with extreme care under the Fig . 66. Contractile lymph -ceils from the 



microscope, Will often show US the Awwr a?i*t of an inflamed eye of a frog. 



cells sketched in fig. 66 (pus-corpuscles). These seldom or never appear 

 of simple spheroidal figure, but almost always under a variety of jagged 

 shapes, whose points and angles are engaged in an incessant change OJL form, 

 usually very sluggish, but at times somewhat energetic. We are able to 



