804 Transactions of the American Institute. 



tents of the cells of living plants, the close chemical resemblance of 

 which to the essential constituents of living animals is so strongly 

 indicated by Payen. And through the twenty-five years that have 

 passed, since the matter of life was first called protoplasm, a host of' 

 investigators, among whom Cohn, Max Schulze and Kiihe, must be 

 named as leaders, have accumulated evidence, morphological, physio- 

 logical and chemical, in favor of that " immense unite de composition 

 elementaire dans tous les corps vivants de la nature," into which 

 Payen had, so early, a clear insight. 



As far back as 1850, Colin wrote, apparently without any know- 

 ledge of what Payen had said before him : 



" The protoplasm of the botanist, and the contractile substance and 

 sarcode of the zoologist must be, if not identical, yet in a high degree 

 analogous substances. Hence, from this point of view, the difference 

 between animals and plants consists in this, that, in the latter, the 

 contractile substance, as a primordial utricle, is inclosed within an 

 inert cellulose membrane, which permits it only to exhibit an internal 

 motion, expressed by the phenomena of rotation and circulation, 

 while in the former it is not so inclosed. The protoplasm in the 

 form of the primordial utricle is, as it were, the animal element in 

 the plant, but which is imprisoned and only becomes free in the ani- 

 mal ; or, to strip of! the metaphor which obscures the simple thought, 

 the energy of organic vitality which is manifested in movement is 

 especially exhibited by a nitrogenous contractile substance, which in 

 plants is limited and fettered by an inert membrane, in animals 

 not so."* 



In 1868, thinliag that an untechnical statement of the views 

 current among the leaders of biological science might be interest- 

 ing to the general public, I gave a lecture embodying them in Edin- 

 burgh. Those who have not made the mistake of attempting to 

 approach biology either by the high a priori road of mere philo- 

 sophical speculation, or by the mere low a posteriori lane offered by 

 the tube of a microscope, but have taken the trouble to become 

 acquainted -with well ascertained facts and with their history, will 

 not need to ba told that in what I had to say " as regards protoplasm," 

 in my lecture " On the Physical Basis of Life," there was nothing 

 new ; and, as I hope, nothing that the present state of knowledge 

 does not justify us in believing to be true. 



As we have seen, the study of yeast has led investigators face to 

 face with problems of immense interest in pure chemistry, and in 



* Colin, Ueber Protococcus pluvialis, in the "Nova Acta for 1850. 



