84 NATURE AND LIFE. 



pletely sheathed in the former. The lymph circulates with 

 its globules between the inner surface of the lymphatic and 

 the outer surface of the capillary, which occupies the cen- 

 tre. The texture of the marrow of the bones, the placenta, 

 the umbilical vesicle, the skin, the arteries, the pancreas, 

 has been illuminated with strong light by the investiga- 

 tions of the same observer. It may even be said that, of 

 the thirty tissues of the system, there is not one whose 

 nature is not better understood through his labors. And 

 this work performed has suggested another to him : we 

 mean the comparison of the same organic parts with each 

 other at different times in their existence ; that is to say, 

 the establishment of general comparative anatomy. In this 

 vast field of histological comparison, so little explored be- 

 fore his time, Robin has collected many precious truths for 

 the general science of biology. 



We have seen that the normal tissues of the organism 

 consist of a fundamental anatomical element and of a cer- 

 tain number of accessory elements. Medical art has gained 

 wholly unexpected light from the discovery of this order 

 of facts. The works of modern micrographers, particularly 

 those of Hannover, Lebert, Virchow, Robin, Broca, Follin, 

 etc., have proved, in fact, that all morbid growths, and 

 especially those known under the names of tumors, cysts, 

 polypi, cancers, tubercles, and scirrhous growths, proceed 

 merely from the superabundant, excessive formation of 

 some one of these accessory elements. It is now demon- 

 strated that those new formations, so often repulsive in ap- 

 pearance, and concealing the seeds of death, contain nothing 

 which is foreign to the organization in its sound state, and 

 are not characterized by any peculiar substance produced 

 under the influence of the disease. They are due some- 

 times to hypergenesis, that is, to an unusual collection of 

 some accessory element taking part in the regular composi- 

 tion of the tissue in which they are developed ; sometimes 



