276 PLANT AND ORGANIC CHEMISTRY 



pounds peculiar to them, and found in only one family, or in 

 species closely allied to it. 



Broadly speaking, the study of plant life cannot be confined 

 within the limits of the vegetable cells, since its radiations reach 

 to the domains of mineralogy and animal life. From a chem- 

 ical point alone it would be difficult to discriminate in every 

 case between the plant and animal cell. The series of animal 

 gums, carbohydrates, alkaloids, and coloring-matters find 

 their analogous series in plants. By the study of embryology 

 it is found that alantoin occurs in animal and plant life, also 

 glycogen and inosite are found in both kingdoms, and the se- 

 cretion of some plant-leaves is a fluid chemically like the ani- 

 mal gastric juice. 



M. Leo Errera, 1 in a recent paper on a fundamental condi- 

 tion of equilibrium of living cells, calls attention to the thin and 

 plastic condition of plant as well as animal cells at the moment 

 of their formation, and their tendency to assume a form which, 

 under the same conditions, an imponderable lamina of liquid 

 would take, and he attributes to this fact their adaptability and 

 the facility with which they change. He believes that we can 

 trace to this cause the great number of organic forms, and for 

 the first time unite the architecture of the cell to molecular 

 physics. Only with age the cell-membrane becomes thick and 

 offers a considerable resistance. 



It may be suggested that this fact is further exhibited when 

 applied to the conditions obtained when plants pass from their 

 younger to older stages; again, it is seen on comparing the lower 

 plastic protoplasmic plants with the rigidity and firmness of the 

 tissues of the higher plants, and in the change from the semi- 

 fluid to the formed and fixed states of chemical compounds. 



The law of progression is one that regards the general good 

 to the disregard of the individual; since in the death or fixation 

 and crystallization of individuals the vegetable kingdom, on the 

 whole, has ascended to its highest present living form, and many 

 of its constituent chemical parts had long ago reached their 

 pinnacle in the cycle of evolution. This concerns equally the 

 changes in the vegetable-cell, and its complex molecule of pro- 



1 Comp. Rend., t. xiii, 1886, p. 822. 



