October 7, 1920] 



NATURE 



171 



other, for many of its contributors have made 

 highly important additions to our knowledge of 

 the growing- embryo. The volume is issued by 

 the Carnegie Institution of Washington, under 

 the aegis of which Prof. Mall had established a 

 department of embryology two years before his 

 death. 



In these essays we see employed the exact 

 technique which Prof. Mall learned when working 

 under the late Prof. His, of Leipzig, but in 

 addition there is evidence of a clear realisation 

 that embryology is a series of vital processes, 

 and that to understand them the living as well as 

 the dead embryo must be studied. The develop- 

 ing chick lends itself particularly well for vitalistic 

 observation, but we have every reason to suppose 

 that the earlier stages of mammalian development 

 — including the early stages in the growth of the 

 human ovum — can be investigated in a similar 

 manner. In this respect a return has been made 

 to the earlier methods of Harvey and of Hunter. 



As examples of the vitalistic method of observa- 

 tion, we may cite papers by Prof. Florence Sabin 

 on "The Origin of Blood-vessels and of Red Blood 

 Corpuscles," by Dr. Eliot R. Clark and Eleanor 

 L.Clark on "The Origin and Early Development 

 of the Lymphatic System," and by Dr. Margaret 

 R. Lewis on " Muscular Contraction in Tissue 

 Cultures." Prof. Sabin shows that blood-vessels 

 arise from islets, or groups, of angioblastic cells, 

 which by canaliculisation and inosculation unite 

 to form a capillary network. The angioblastic 

 cells give rise to the endothelial lining of blood- 

 vessels, and both the angioblasts and endothelial 

 cells can, and do, produce nucleated red blood 

 corpuscles. The lymphatic system of vessels, 

 however, as one is led to infer from the experi- 

 ments of the two Clarks, arises from the endo- 

 thelium of the veins in certain embryonic regions, 

 and from these regions, or centres, the endothelial 

 outgrowths invade certain neighbouring areas of 

 the body and thus provide it with a lymphatic 

 system. If one centre of outgrowth is destroyed, 

 neighbouring centres will supply the deficiency. 



Another series of papers records observations on 

 the vital reactions of certain cells in the body of 

 adult animals. Capt. Charles Essick found that 

 when a solution containing fine particles was 

 placed in the sub-arachnoid spaces of the brain 

 of a living animal the endothelial cells of these 

 spaces were transformed into phagocytes, which 

 consumed the foreign matter thus introduced. 

 Capt. Essick's investigation was occasioned, appa- 

 rently, by observations made by Capt. Lewis H. 

 Weed during a research on "The Experimental 

 Production of Hydrocephalus " — an important 

 NO. 2658, VOL. 106] 



inquiry which also appears in this memorial 

 volume. To this series also belongs the paper 

 contributed by Dr. Charles C. Macklin on "The 

 Development and Function of Macrophages in 

 the Repair of Experimental Bone-wounds Vitally 

 Stained with Typan-blue." We infer from 

 Dr. Macklin 's experiments that the phagocytes 

 which appear at the sites of repair and of rapid 

 growth have, as their chief business, the con- 

 sumption of tissue-debris and the rendering of that 

 ddbris fit for return to the general circulation of 

 the body. Dr. George Corner's observations on 

 "The Widespread Occurrence of Reticular Fibrils 

 produced by Capillary Endothelium " serve to 

 enhance the functional importance of the cells 

 which line blood and lymphatic vessels. 



Besides these papers on the living behaviour of 

 the tissues of the body, this volume contains 

 important contributions to orthodox or morpho- 

 logical embryology — particularly a most valuable 

 summary of the present state of our knowledge 

 of the youngest known human embryos, given by 

 Prof. George L. Streeter, who succeeded Prof. Mall 

 as director of the department of embryology in 

 the Carnegie Institution of Washington. Dr. 

 Warren H. Lewis's description of the skull of a 

 human foetus towards the end of the second month 

 of development is also a very welcome addition to 

 our knowledge of the human body. Other papers, 

 like those of Prof. C. R. Bardeen on "The Post- 

 natal Development of the Human Body," Prof. 

 Robert Bean's on "The Post-natal Growth of the 

 Heart, Kidneys, Liver, and Spleen of Man," and 

 Dr. Schultz's " Development of the External Nose 

 of Whites and Negroes," represent contributions 

 to anthropology as well as to embryology. .Mto- 

 gether, this volume represents a worthy memorial 

 to a really great man. 



Two Books for the Country. 



(i) Springtime and Other Essays. By Sir Francis 

 Darwin. Pp. vii -f- 242 -(- viii plates. (London: 

 John Murray, 1920.) Price 7s. 6d. net. 



(2) Memories of the Months. Sixth series. By the 

 Right Hon. Sir Herbert Maxwell, Bart. Pp. xi 

 -f3i4. (London : Edward Arnold, 1919.) Price 

 7*. 6d. net. 



(i)OlR FRANCIS DARWIN'S essays have a 

 »J peculiar charm ; the reader is caught in 

 the current of the author's enjoyment. Unin- 

 fluenced by artifice, we find ourselves sharing in 

 his pleasures, and, to begin with, in the delight of 

 the spring renascence. "The spring is the hap- 

 piest season for those who love plants, who delight 

 to watch and record the advent of old friends as 



