66 GENERAL ANATOMY OF THE TISSUES. 



water, 68-88 ; hsematin, 1-67 ; globulin and membranes, 28-22 ; fat. 0-23 ; 

 extractive matters, 0-26; mineral substances (without iron), 0-81; of 

 which chlorine, 0-16 ; sulphuric acid, 0-006 ; phosphoric acid, 0-4 ; 

 potassium, 0-83; sodium, 0-10; oxygen, 0-06; phosphate of lime, 0-01 ; 

 phosphate of magnesia, 0-007. To these must also be added, free oxygen 

 and carbonic acid, which likewise occur in the yelk. 



We have here instances of cells containing much protein, and espe- 

 cially fat, and may consider them to be fair examples of this kind of cell. 

 The comparison of the contents of these cells with the plasma of the 

 blood, out of which those of the one kind are formed, while the others 

 live in it, is very interesting. In the blood-globules there is a consider- 

 able preponderance of solid constituents, since the blood-plasma only 

 contains about 10 per cent, of solids, which is evidence that there are 

 cells whose contents do not attain an equilibrium with the cytoblastema 

 by which they are supported. With regard to particular substances, 

 the blood-corpuscles contain more fat ; hsematin, which is not found in 

 the plasma; more potassa and phosphoric acid; less chlorine, extractive 

 matters, soda, and earths. The yelk of the hen's egg contains also con- 

 siderably more solid constituents than the blood, which however is here 

 less surprising than in the blood-corpuscles which swim in the blood- 

 plasma. It is interesting, that the relative proportions of the different 

 substances are quite different in this case from the other. We have, 

 namely, an exceedingly large quantity of fat, more protein and salts ; 

 and among the latter, again, more potassa, and also more earthy salts. 



Even these facts indicate a considerable independence of action in 

 the cells ; but those which have been lately made known by Ludwig, 

 tend still more forcibly in the same direction ; for the influence of the 

 nerves upon the salivary glands discovered by this observer must, I 

 believe, be so interpreted, that it is not only the membranes propriss 

 of the vesicles of the salivary glands, which are so altered in their mole- 

 cular relations by the nervous influence that they directly exercise an 

 energetic attraction upon the blood-plasma which surrounds them, but 

 the epithelial cells which line them also. If this really be the case, we 

 have an insight into an altogether new condition regulating the absorp- 

 tive powers of cells, and at the same time cell-life is brought into such 

 connection with the activity of the nervous system, that it no longer 

 appears out of reason to speak of the positive functions of the latter. 

 Such relations are in nowise opposed to analogy, since in the contrac- 

 tile elements we have already a connection between nervous activity 

 and the modification of cell-contents, which perhaps upon further inves- 

 tigation may come under the same general category as the foregoing. 

 In any case, these considerations lead anew to an exact investigation of 

 the molecular forces of cells, especially of those electrical phenomena 

 which will certainly be found in them. 



