48 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



The following figures represent the behavior of the muscular tissue 

 to solutions of different salts (Ranke) : 



MAXIMUM IMBIBITION. 



1 PER CENT. Na'Cl. 1 PER CENT. K Cl. 



Living, resting muscle, . Positive, but not capable of 



estimation, as the muscle 

 instantly died. 



Living, tetanized muscle, . 13 Positive : not to be estimated, 



for the same reason as above. 

 Dead muscle, . . .35 136 per cent. 



Perfectly analogous observations have also been made in the case of 

 the nervous tissues. 



It would, therefore, appear that living tissues only absorb by 

 imbibition when their vital forces are diminished in energy. In the 

 organism the cells are continually bathed in a fluid which contains the 

 matters necessary for the nutrition of the cells. If the cells have been 

 at rest their nutritive equilibrium lias not been disturbed and imbibition 

 does not take place. If, however, they are exhausted by previous 

 activity, imbibition is then inaugurated, nutritive substances enter, the 

 results of cell activity are extruded (acids, etc.), nutritive equilibrium is 

 restored, and imbibition not only ceases, but from the increased volume 

 of the cell-contents pressure is produced on the cell-membrane and the 

 excess of fluid is forced through again to the exterior b} T filtration. 

 Consequently cells which are most weakened by prolonged activity are 

 the cells which carry on t as a direct result of the chemical affinities 

 created by that activity, the most active imbibition. By these peculi- 

 arities in the conditions which govern imbibition in living cells is to be 

 explained the peculiar distribution of the inorganic salts in the animal 

 bod} T , sodium in the fluids, potassium in the solid organs of the body. 

 For, as we know, sodium solutions are indifferent fluids and are not 

 absorbed by the tissues unless they have undergone some depression in 

 energy, while potassium salts in solution are rapidly absorbed and lead 

 to the death, the drowning out of protoplasm. 



6. FILTRATION OR TRANSUDATION is the passage of fluid through a 

 membrane dependent upon inequality of hydrostatic pressures ; but that 

 a fluid should so pass it is essential that the membrane be capable of 

 absorbing the fluid by imbibition. 



The greater the affinit}^ of the fluid for the membrane (see Imbibition} 

 the more rapidly will the fluid under a moderate pressure pass through 

 the membrane: thus water, or even a saline solution, will filter more 

 rapidly than oil. Filtration will occur more rapidly through a thin than 

 a thick membrane. 



The rapidity of filtration is, further, in direct proportion to the pres- 

 sure which the fluid exerts on the membrane, and increases with increas- 



