and Laboratory Methods. 1^^^ 



life a steady diminution in the relative amount of the additions to the size and 

 weight of the body in successive years after birth. The same is true of the 

 organs and tissues except in the case of those which are largely made of 

 " Blastzellen." Such tissues, as for instance the epithelial lining of the alimentary 

 canal, continue to grow by the multiplication of cells until nearly the time of 

 death. The reason for the greater absolute weight of an adult man over that 

 of an infant is found in the fact that the muscular and skeletal systems take on 

 weight by processes of cell metamorphosis essentially regressive in character, 

 there being in these cases no growth by cell multiplication after early life. 



The work is one of value on account of the mass of data on the growth of 

 the human body which it presents. While it is probable that few would agree 

 with all the theories proposed, the discussion nevertheless brings out strongly the 

 possible importance of cell nutrition as a factor in developmental processes. 



R. p. 



Bataillon, E. La pression osmotique et les The general standpoint of the author 

 grands problemes de la Biologie. Arch. f. " 



Entwick.-mech, II: 149-184, pi. 5, igoi. is that osmotic pressure is a general 



and fundamental factor in biological phenomena, and should furnish the basis 

 for the investigation of such important problems as the resistance of organisms 

 to dehydration (latent life,) teratogeny, the production of multiple embryos, and 

 artificial parthenogenesis. On all these points experimental results are offered. 

 The first experiments discussed are on the extraordinary ability of Ascaris eggs to 

 resist the action of fixing agents and other poisonous fluids. The reasons for 

 this resistance capacity are found in the facts that the egg is surrounded by 

 a membranous chorion which is semi-permeable, and that the fluid of the interior 

 of the egg is of such a concentration as to furnish a very high osmotic pressure. 

 On account of this high osmotic pressure ordinarily harmful substances cannot 

 enter the egg. There is no plasmolysis of the egg in the fluids of less osmotic 

 pressure than that of a 15 per cent, solution of NaCl. The eggs are unable to with- 

 stand the dehydration produced by a 30 per cent, solution of NaCl. The 

 author thinks that cases of " latent life," of which desiccated rotifers form a good 

 example, are to be explained as a result of the great osmotic pressure of their 

 body substance which resists the extraction of water beyond a certain point. 



Loss of water is found to have a retarding influence on development and 

 may completely stop it. The eggs of Petromyzon Planeri show no segmentation 

 in a 1 per cent, solution of NaCl, while in a .2 per cent, solution their development 

 proceeds normally. In solutions of intermediate concentrations there are varying 

 degrees of retardation. Solutions of CaCl2 and sugar isotonic with the NaCl were 

 tried and the same results were obtained, indicating that the osmotic pressure is 

 the important factor rather than the chemical composition. Twin larvse of 

 Petromyzon were obtained by placing the fertilized eggs for a certain time (about 

 eighteen hours) in solutions isotonic with 1 per cent. NaCl and then removing 

 them to water, in which the development took place. Fertilized eggs of the 

 teleost Leucisciis rutilus treated in the same way (except that they were kept in 

 the solution only one hour) developed into multiple monstrosities. 



By the use of the same method, with variations in the time of action of the 

 solution, the author obtained segmentation of unfertilized eggs of some fish and 



