MICROSCOPICAL EXAMINATION. 127 



bile-pigments in all probability occur under the same modification, 

 which, according to Berzelius and Scherer, is to be regarded as 

 the final product of the metamorphosis of cholepyrrhin. 



Taurin has often, although not invariably, been detected by 

 Frerichs* in the whole course of the intestinal canal, and even in 

 the solid excrements. 



The constituents of the intestinal canal insoluble in water, 

 alcohol, and ether, fall for the most part within the domain of 

 microscopic inquiry. They essentially consist of undigested or 

 indigestible fragments of food. Among the undigested substances 

 we commonly find not only fat-globules, but starch-granules, fibres 

 of muscle, and fibrills of cellular (areolar) tissue in the excrements 

 after the use of the corresponding articles of food. The starch- 

 granules seem to be diminished in their diameter, and this diminu- 

 tion is the more marked the lower they are found in the intestinal 

 canal ; they usually appear fissured and lobulated, and as if some of 

 their coats were partly or entirely dissolved ; in this case their true 

 nature can often not be detected under the microscope, unless with 

 the aid of a solution of iodine. Muscular fibres are found in 

 every phase of change; we recognise some primitive fibres un- 

 changed in their histological formation, and parallelepipeds of the 

 same structure, in which the striae may be pretty clearly made out, 

 presenting a finely punctated appearance ; the longitudinal striae 

 are usually the most distinct; the sarcolemma has for the most 

 part disappeared ; finally, there often remains merely a tolerably 

 hyaline mass, which can only be recognised as the remains of mus- 

 cular fibre by the parallel grouping of a few prominent points. 

 A complete solution of muscular fibre is not effected by the gastric 

 and other digestive juices, as has also been found by Frerichs. 



Fragments of bone, after being swallowed, may be always 

 detected in the intestine and in the excrements, although a great 

 part of them is obviously dissolved in the primce vice. 



As the histological constituents of the vegetable tissues have 

 the least tendency to be decomposed by the digestive juices, they 

 are always found comparatively little changed after the use of 

 vegetable food ; cellulose is proof against all organic solvents, and 

 hence we meet with all varieties of vegetable cells. The chlorophylle- 

 cells remain unchanged; the parenchyma-cells are only some- 

 times isolated; spiral vessels may be beautifully seen in the 

 excrements both of the higher and the lower animals. Yeast- 

 cells are often met with after the use of pastry. 

 * Op. cit. p. 841. 



