64 GENERAL ANATOMY OF THE TISSUES. 



of hgcmatin, of difierent kinds of pigment, and of fat, are the most 

 obvious. But metamorphoses of the cell-contents are very common in 

 adult animals also, and are at the same time very important, since in 

 many places, on account of the great number of cells which are affected 

 in the same way at the same time, unexpectedly great results are pro- 

 duced, as one of the most important of which we may name the biliary 

 secretion, which is brought about, so to say, only by the activity of the 

 many millions of cells which form the liver. A pretty series of changes 

 may also be traced in the fat-cells, which, according to the deficiency or 

 superfluity of nutritive fluid, in the one case lose their proper contents, 

 and may even become cells containing mere serum, in others are filled 

 to bursting with drops of oil ; again, in the cells of the fat-secreting 

 glands, which at first contain but little fat, and finally become crammed 

 with it ; and also in the lymph-corpuscles, which develop the coloring 

 matter of the blood within themselves, and thus become blood-corpus- 

 cles.* The formation of mucus, again, must probably be assigned to 

 the epithelial cells of the mucous glands and mucous membranes ; that 

 of the so-called pepsin to the cells of the gastric glands ; and that of 

 semen to the spermatic cells. A multiplicity of confirmatory evidence 

 is afforded by comparative anatomy, and I will here only advert to the 

 development of the concretions of uric acid in the renal cells of the mol- 

 lusca, that of sepia in the cells of the ink bag of the Cephalopod, of 

 crystals and concretions of different kinds in the cells of the invertebrata, 

 and of certain pigments in those of the mollusca. Pathological anatomy 

 affords us the pigment formations, the metamorphoses of cells containing 

 blood-corpuscles, and the fatty deposits in cells of all kinds. 



Manifold morphological phenomena go hand in hand with these 

 changes, such as the thickenings of the cell-membrane, which have been 

 already adverted to, with laminated depositions upon their inner surface, 

 and even with the formation of pore-canals ; as the precipitation in the 

 cell-contents of granules of different sorts, as of pigment, albumen, 

 casein (in the yelk, perhaps in the hepatic cells) ; and as the formation 

 of fat drops, of elementary vesicles, of concretions, crystals, and nuclei. 

 Even movements resembling the cyclosis of plants appear to occur in 

 the cells of the lower animals (seen by me in the cells of the arms of a 

 minute Medusa, a new u3^gmopsis from the Mediterranean, and of Poly- 

 clinum stellatum), and in Protozoa (currents in Loxodes bursaria, con- 

 tracted vesicles in different genera) ; while on the other hand, the Brownian 

 molecular movements, i. e. a more or less active tremulous motion 

 of granules without further change of place, which may be observed in 

 many cells under the microscope, most beautifully in the pigment cells 

 of the eye, are also, perhaps, hardly to be reckoned among vital pheno- 

 mena. 



* [In the oviparous vertebrata — Tks.] 



