518 



SCIENCE. 



[N. S. Vol. V. No. 117. 



in accepting the view that glycogen is a reserve 

 material of primary importance in the growth 

 and development of new tissues, but it may well 

 be considered whether the theory formulated 

 by Barfurth, that the glycogen so abundant in 

 new growths is a bye-product resulting from 

 the cleavage of complex proteids, ready to be 

 again utilized or stored up as reserve material 

 as occasion demands, is not more consistent 

 with present knowledge than the assumption 

 that glycogen contributes somewhat to the 

 building up of the tissues ' without losing its 

 own molecular identity,' or that it is employed 

 in the growth and development of the tissues 

 without becoming part of them. The very 

 nature of glycogen — certainly, as we ordinarily 

 use the term — is opposed to the stability as- 

 sumed in the preceding quotation. Far more 

 plausible is the assumption that glycogen is a 

 prominent product of metabolic activity, and as 

 such may be widely formed in all developing 

 tissues, while in the absence of circulating blood, 

 which precludes its immediate removal, it may 

 accumulate for a time in the growing tissues, 

 doubtless being used again in the construction 

 of fresh protoplasm. Indeed, it is so readily 

 decomposable that it naturally constitutes a 

 valuable pabulum for the nutrition or growth 

 and development of fresh tissue. In this sense 

 we can readily conceive of its importance, both 

 as a measure of some forms of metabolic activity 

 and as an aid to new growth, but wholly as a 

 chemical substance which, like other kindred 

 carbohydrates, can be utilized by the living cells 

 which are of necessity the active agents in all 

 growth. But Dr. Creighton, if we understand 

 him aright, attributes to the glycogen of em- 

 bryonic tissues a kind of intangible power which 

 makes it the forerunner and pioneer of new 

 growths, without loss of its own molecular 

 identity and without becoming an integral part 

 of the tissues. 



Thus, in considering the glycogen so notice- 

 able in primordial cartilage it is stated that 

 ' ' one function of the glycogen of cartilage may 

 be guessed to be the separating out of calcareous 

 salts from the protoplasm in such wise that 

 they become visible in the form of granules or 

 vesicular drops. Of course, by far the most 

 of the calcareous matter of bones must come 



to them direct from the blood ; but there is a 

 period of development, the period of transition 

 from cartilaginous moulds, at which lime salts 

 are deposited independently of the blood and 

 in some unknown manner by the agency of 

 glycogen. Assuming that to be a real office of 

 glycogen within the cells of cartilage, it need 

 not exhaust its functions. The diflfusion of 

 glycogen through the cartilage-protoplast ap- 

 pears to impart to it a certain mobility or dy- 

 namic property, whereby cavities are hollowed 

 out in the matrix and the partitions absorbed 

 in aid of the formation of the central space 

 which the blood-vessels enter and possess. 

 Even when all trace of cartilaginous structure • 

 is lost, it appears probable that some of its 

 protoplasm, still occupied by glycogen, is util- 

 ized in the form of ostoclasts for the further 

 modelling of the medullary canal or the can- 

 cellous tissue. These various uses of glycogen, 

 or purposes to which it may be put, are con- 

 sistent with the view of it as an intra-cellular 

 or parenchymatous medium, doing duty for a 

 time, or in occasional circumstances, in place 

 of the great internal medium, namely, the blood 

 itself" This somewhat lengthy quotation is a 

 good illustration of the character of the activity 

 or dynamic power which Creighton constantly 

 attributes to the glycogen present in embryonic 

 tissues. To the unbiased reader, however, it 

 would seem that such conclusions are hardly 

 warranted, although it is possible that, in the 

 pathological part to follow the present volume, 

 additional facts will be presented which may 

 tend to strengthen the author's peculiar views. 

 Glycogen may well be considered in the above 

 tissue as a pabulum, which, like the blood itself, 

 furnishes material necessary for the growth and 

 activity of the developing cells, but we fail to 

 see why it should be necessary to attribute to 

 the glycogen a special formative power so radi- 

 cally different from that heretofore attributed 

 to carbohydrate matter in general; a formative 

 power which raises the Intra-cellular glycogen 

 to the plane of living protoplasm itself. Its 

 presence in the protoplasm may give to the 

 latter increased activity, may indeed endow it 

 with peculiar and exceptional power for the 

 time being, but it seems far more consistent to 

 consider that the true formative power resides 



