EXAMPLES OF TISSUE-PRODUCTS. 5 



past and its future to the pabulum from which it was formed, 

 and to the products into which it is ever changing. 



(4.) Of late years the chemistry of animal products has made 

 very great advances. In the table before you are written up the 

 names and somewhat complicated formula of a few of these 

 compounds, most of which occur in the animal body, as results 

 of the natural metamorphosis of its several tissues. Now, de- 

 spite the complexity of many of these bodies, the intimate con- 

 stitution of even the most complicated of them is fairly well 

 understood, and in many cases so well understood that the bodies 

 themselves can be actually built up by the chemist in his 

 laboratory without having any recourse whatever to organic 

 nature. 



Anima 1 Products 

 C H s N Methylamine 



Let me direct your attention to one or two of these more par- 

 ticularly. Here, for instance, is leucine, a white crystalline 

 body, consisting of 6 atoms of carbon, 1 3 of hydrogen, i of ni- 

 trogen, and 2 of oxygen. Now, leucine is a product of the use, 

 and consequent waste or metamorphosis, of glandular tissue. It 

 is found in decoctions of glandular tissue, more particularly of 

 the spleen and pancreas; and also occurs occasionally as an 

 abnormal constituent of urine. It may be made artificially in the 

 flask or crucible by the breaking up of muscle, ligament, skin, 

 horn, hair, feathers, and a variety of other animal substances ; 

 but so well is the constitution of this complex tissue-product 

 understood, that leucine can now be formed, not only destructively 

 by the breaking up of more complex bodies, but constructively 

 by a synthesis of less complex organic bodies quite independently 



