ELEMENTS OF STRUCTUKE. 



67 



matters of completely different characters; thus the body of the blood- 

 corpuscle is found to be made up of a transparent yellow gelatinous sub- 

 stance (fig. 47); in old scaly cells also, such as are met with on the 

 surface of many mucous membranes (fig. 48), the protoplasm is replaced 



Fig. 47. Human blood-corpusclea. 



Fig. 48. Old epithelium cells from the 

 human mouth. 



by a hard substance, poor in water, and almost destitute of granular matter, 

 a metamorphosed albuminous material, to which the name of keratin 

 has been given. 



Such cells, however, as those in both instances cited, are no longer 

 capable of supporting a prolonged existence, they have lost their active 

 vitality with their protoplasm. 



Again, there are cells still more fre- 

 quently met with which contain other 

 substances as formed deposits in their pro- 

 toplasm (fig. 49). 



Setting aside for the present those cells 

 into whose bodies foreign matters, such as 

 granules of carmine (a), or blood-corpuscles 

 and fragments of the same (&), have pene- 

 trated from without (remarkable objects Fig> 49 ._ Cel]s ^deposits of foreign 

 which will be considered at greater length 

 presently), we frequently meet with globules 

 and drops of neutral fats laid down in the 

 original cell-mass (d), which may gradually 

 coalesce, supplanting the protoplasm until 

 but a small remainder of it is left. Besides 

 such fatty matters, molecules of brown 

 biliary pigment are to be seen in other cells, as, for instance, in those 

 of the liver (c). 



Cells also which have become the receptacles of 9 melanin granules 

 (p. 52) present the most peculiar appearance. This pigment may be pre- 

 sent in such abundance that the whole body of the cell becomes black 

 throughout (fig. 50). The occurrence of crystals in the interior of animal 

 cells is less frequent. They are, however, to be met with as acicular for- 

 mations, already alluded to (p. 27), and appear in the interior of fat cells 

 on the post mortem cooling of corpses, within the membranes of the 

 former (fig. 51). But while the appearance of these is by no means rare, 

 there are other crystalline deposits which are only encountered in minute 

 quantity, and under abnormal pathological conditions. Matters which 

 assume the crystalline form in such watery solutions as exist in the animal 

 economy, must be regarded generally as unfitted to take part in the con- 



matter in their protoplasm (half dia- 

 grammatic), a, a lymph corpuscle with 

 granules of carmine imbedded in it; 

 6, another of the same, with included 

 blood-cells and fragments of the latter 

 c, an hepatic cell, containing fat globules 

 and granules of biliary pigments; rf, 

 a cell with fat globules and distinct 

 membrane; e, another, with granulesof 

 melanin. 



