DIGESTION 329 



adjunct to its specific work. But this is not the whole truth. 

 The gland-cell is not a mere filter through which water and 

 salts pass in the same proportions in which they exist in the 

 liquids that the cell draws them from. The secretions of 

 different glands differ in the nature, and especially in the 

 relative proportions, of their inorganic constituents ; and the 

 secretion of one and the same gland is by no means constant 

 in this respect, as we shall have to note more especially 

 when we come to deal with the influence of the nervous 

 system on secretion (p. 338). 



The proteid substances, such as serum-albumin and 

 globulin, common to blood and to some of the digestive 

 secretions, take a middle place between the constituents that 

 are undoubtedly manufactured in the cell and those which 

 seem by a less special and laborious, though a selective, 

 process to be passed through it from the blood. Their 

 absence from bile, and, as we shall see, from urine, their 

 abundance in pancreatic and scantiness in gastric juice, point 

 to a closer dependence upon the special activity of the gland- 

 cell than we can suppose necessary in the case of the salts. 



Although it is in the cells of the digestive glands that the 

 power of forming ferments is most conspicuous, it is by no 

 means confined to them. It seems to be a primitive, a 

 native power of protoplasm. Lowly animals, like the 

 amoeba, lowly plants, like bacteria, form ferments within the 

 single cell which serves for all the purposes of their life. 

 The ferment - secreting gland-cells of higher forms are 

 perhaps only lop-sided amoebae, not so much endowed with 

 new properties as disproportionately developed in one 

 direction. The contractility has been lost or lessened, the 

 digestive power has been retained or increased; just as in 

 muscle the power of contraction has been developed, and 

 that of digestion has fallen behind. The muscle-cell and the 

 cartilage-cell are parasites, if we look to the function of 

 digestion alone. They live on food already more or less 

 prepared by the labours of other cells ; and it is a universal 

 law that in the measure in which a power becomes useless it 

 disappears. But the presence of pepsin in the white blood- 

 corpuscles, the parasites as well as the scavengers of the 

 blood, and of amylolytic ferments in many tissues, should 



