PREFACE. V 



constituent of :i vast number of forms of plant life, but its role in vital processes, 

 while, on the whole, as essential to the continuance of life, is of an entirely different 

 character. Moreover, the general and special characters of these substances in 

 relation to those of the bodies which originate them, and the mechanisms of their 

 formation, are likewise strikingly diff(>rent. Hemoglobin constitutes nearly the 

 whole of the erythrocyte or red-blood corpuscle, and that portion of the ery- 

 throcyte which is not this substance may properly be regarded as being in the 

 nature of an adjunct, but nevertheless essential. In early embryonic life the 

 erythrocytes are nucleated and probably derived directly from the mesoblastic 

 elements, and they increase in number by mitosis. Later, proliferation occurs in 

 all parts of the circulation, in certain capillary areas more than others, especially 

 in those of the liver, spleen, and bone-marrow. During the progress of fetal devel- 

 opment the erythrocytes, primarily spherical and nucleated, in time lose their nuclei, 

 and become smaller, and take on the peculiar disk or cup-shaped form of postnatal 

 life. After birth the red bone-marrow is the chief or sole seat of formation of erythro- 

 cytes. It is the common conception that in this structure these corpuscles arise 

 from nucleated red cells which exist at first as colorless, nucleated erythroblasts, 

 and subsequently as smaller, denser, colored, nucleated normoblasts. The former, 

 which are looked upon as the hereditary representatives of the embryonal erythro- 

 cytes, are generally conceived to be converted into normoblasts by mitosis, and 

 the latter in turn to become ordinary erythrocytes upon the disappearance of the 

 nuclei by solution or extrusion. It is, however, more likely, as suggested in 1882 by 

 Malassez, and very recently (1912) by the investigations of Emmel by means of 

 plasma cultures, that the erythrocyte of late fetal and post fetal life is formed from 

 the cytoplasm of the erythroblast by a simple process of budding and detachment. 

 According to either conception the erythrocyte is a separated portion of the mother 

 substance that has been set free in a highly specialized life-sustaining medium, but 

 in a distinctly modified form, inasmuch as it has a much higher hemoglobin content 

 and is lacking in the amoeboid activities and power of reproduction of the parent 

 substance, the latter differences being readily accounted for in the absence of 

 nuclear matter. Starch, on the other hand, is a synthetic product of metabolic 

 activity which bears no resemblance to the protoplasm that gave rise to it, and 

 which is destined to serve an entirely different purpose from that of hemoglobin 

 in the life-history of the organism. With hemoglobin as it exists associated with 

 the stroma in the erythrocytes we are dealing with an active, living, functionating, 

 highly specialized form of protoplasm; with starch, we deal with an absolutely inert, 

 non-living, non-functionating, extremely complex carbohydrate in the nature of a 

 stored-up pabulum, and a synthetic product of plastids which are specialized forms 

 of protoplasm. In the hemoglobin research it was shown that the hemoglobin 

 molecule is modified in specific relationship to genus, species, etc., which may 

 be taken to mean that the form of protoplasm that is expressed by the term 

 erythrocyte is correspondingly stereochemically modified; with starch it has been 

 found, as will be seen by the context, that the molecule is likewise changed 

 in specific relationship to genera, species, etc., which accordingly may also be 



