12 GENERAL ANATOMY OF THE TISSUES. 



the black pigment of the eye and of other coloured cells, the 

 granular precipitates of biliary colouring matter, of different 

 salts in the kidneys and in the urine ; lastly, the protein 

 granules (albuminous granules) which are found free in certain 

 portions of the grey substance of the central nervous system 

 and of the retina. Among pathological but very common 

 formations, we must enumerate here amorphous deposits, 

 the colloid granules in the thyroid and elsewhere, and the 

 corpuscula amylacea of the central nervous system, although 

 these sometimes attain a verv considerable size. All these 

 granules want the properties observed in the higher elementary 

 parts, such as endogenous growth, multiplication, assimilation, 

 and excretion, and so far incline towards the purely iuorganic 

 forms — crystals ; which are also found, though less commonly, 

 in the organism, as for example in the spleen, in the lungs 

 (black columns), in the ear, in the cells of the preputial 

 glands of the rat, in the blood-corpuscles of the dog and of 

 fishes, in the fat-cells of man, and in the cells of the chorion of 

 the embryo of sheep. 



Elementary vesicles also occur very frequently, and are 'for 

 the most part allied, physiologically, with the elementary 

 granules, since, once formed they do not increase, and neither 

 multiply by division nor by endogenous development. The 

 milk-globules may with tolerable certainty be arranged among 

 these; at first included within the cells of the nascent milk, 

 they are subsequently found free, in enormous numbers, in the 

 perfect secretion and, as Henle first stated, consist of the 

 fatty matter of the milk, with an investment of casein. The 

 immeasurably small molecules of the chvle and of the blood, 

 are also, according to H. Muller's investigation, fat globules 

 with a protein envelope, and similar vesicles may be found in 

 most other fluids containing fat and albumen in abundance. 

 In fact, since the discovery of Ascherson Qluller's f Archiv/ 

 1840, p. 49), that whenever fluid fat and fluid albumen are 

 shaken together, the fat globules which are formed always 

 become surrounded by an albuminous coat, it is more than pro- 

 bable that whenever, in the body, fat and albumen in the fluid 

 condition come into contact, similar vesicles are produced. 



A peculiar class of elementary vesicles is formed by the 

 elements which occur in the velk of certain animals. "We are 



