Maech 26, 1897.] 



SCIENCE. 



517 



scribed polygon we may ■wish to use.' The ex- 

 ample in question refers to a problem, to in- 

 scribe in a circle a regular polygon of any 

 given number of sides. 



Floeian Cajoei. 

 CoLOEADO College, 



CoLOEADO Speings, March 2, '97. 



SCIENTIFIC LITERATURE. 

 Microscopic Researches on the Formative Property 

 of Glycogen. Part I., Physiological. By 

 Chaeles Creighton, M.D., Formerly Dem- 

 onstrator of Anatomy at Cambridge. London, 

 Adam and Charles Black. 1896. With five 

 Colored Plates. Pp. 152. 

 Dr. Creighton's work, as stated in the preface 

 to the present volume, has been directed espe- 

 cially to the problem of glycogen in the forma- 

 tive processes of disease, but it was found neces- 

 sary to turn aside at numerous points in search 

 of a physiological basis or paradigm, and as a 

 result we have the present volume, dealing 

 mainly with the bearing of glycogen on normal 

 growth. Emphasis is laid upon the fact that the 

 glycogen of animal tissues is not destined solely 

 for conversion into sugar, but that in embryonic 

 formations, as well as in pathological new 

 growths, glycogen presents itself in its tissue- 

 making, not its sugar-yielding character. Dr. 

 Creighton's microscopic studies lead him toward 

 the somewhat broad generalization ' ' that the 

 formative property of glycogen is analogous to 

 or parallel with that of hsemoglobin; * * * 

 that glycogen plays the part of a carrier to the 

 tissues; that it contributes somewhat to the 

 building up without losing its own molecular 

 identity; that it is present at the formation of 

 tissues and employed therein without becoming 

 part of them, and that it acts thus, in some cases 

 as the precursor or deputy of hsemoglobin, and 

 until such time as the vascularity of the part is 

 sufficiently advanced ; in other cases as the sub- 

 stitute of haemoglobin from first to last — in 

 those tissues which are built up in whole or in 

 part without direct access of blood." 



The observations which lead to this some- 

 what startling view are made upon tissues, or- 

 gans or whole embryos, usually fixed in potas- 

 sium bichromate and hardened in absolute 

 •' alcohol, the presence or absence of glycogen 



being determined in the sections of tissue by 

 the usual method of treatment with a weak so- 

 lution of iodine in potassium iodide. Attention 

 is called to the fact that methyl-violet, contrary 

 to the view frequently held, also gives a distinc- 

 tive reaction with glycogen, the dye picking 

 out the spots of glycogen from all other parts of 

 the section as distinctively as iodine itself. This 

 method, however, possesses no practical advan- 

 tages over the iodine method. 



Dr. Creighton has studied especially the re- 

 lation of glycogen to the growth of the bronchial 

 tree and of the choroid plexuses ; its relation 

 to the formation of the renal tubules and the 

 development of the intestinal mucous mem- 

 branes ; its distribution in foetal hoof, nail and 

 hair, and in the developing and functional stri- 

 ated muscular fibre ; its relation to the enamel- 

 ling and cementing of teeth ; its presence in 

 cartilage and in the developmental and other 

 immature secretions of the mammary glands, 

 etc. As noted by many previous observers, 

 glycogen is found to be especially prominent in 

 these young embryonic tissues, especially at the 

 centers or points of rapid growth, and at a time 

 in fcBtal life when the vascularity of the part is 

 limited or not even established. The point, 

 however, upon which most stress is laid is that 

 glycogen is the dynamic principle in the de- 

 veloping tissue ; in epithelial cells, for exam- 

 ple, as in the formation of the renal tubules, 

 the glycogen being the precursor of hsemoglobin 

 as a formative agent. Thus, in the tubular 

 formation within the kidney the advancing and 

 differentiating epithelium is supposed to depend 

 mainly, if not solely, upon resources contained 

 within itself, i. e., the glycogen, pending the 

 complete establishment of vascularity, when 

 the glycogen disappears. Similarly, in the 

 muscular tissue of active or mature life, glyco- 

 gen, like the hsemoglobin, is looked upon as a 

 reserve store for emergencies. Although not 

 essential to the activity of the muscle, it may, 

 perhaps, says Creighton, take the place of the 

 circulating blood in one way as the store or 

 reserve of hsemoglobin does in another, or 

 possibly there may be muscles in which the 

 reserve is chiefly haemoglobin, and others in 

 which the reserve is mainly glycogen. 



The physiologist has no hesitancy whatever 



