380 



Glossary 



given point, usually some defi- 

 nite feature, as the attachment 

 of a muscle, taken as a point of 

 reference. 



DORSO- VENTRAL. A term much 

 used in the anatomy of th2 

 higher animals to signify a di- 

 rection from-back-to-belly of a 

 creature. 



DUODENUM. The first portion of 

 the small intestine between tha 

 stomach and the jejunum. 



DYXAMIC CENTER. A phrase used 

 rather frequently in recent biol- 

 ogy, especially in the biology of 

 the cell, to express the concep- 

 tion that certain structures, as 

 the centrosome, are in someway 

 not clearly specifiable the "seat" 

 of various vital activities. The 

 phrase has some such implica- 

 tion for general physiology as 

 "nerve center" had and with 

 many still has, for nerve phys- 

 iology. 



ECOLOGICAL. Pertaining to Ecol- 

 ogy, the science of organisms in 

 relation to their natural environ- 

 ments. This old but newly ap- 

 preciated and named branch of 

 the science of living nature, may 

 properly be regarded as the nat- 

 ural history of plants and ani- 

 mals modified to meet the mod- 

 ern demands of comprehensive- 

 ness and exactness in dealing 

 with a great province of nat- 

 ural phenomena. 



ECTOPLASM. The outermost, some- 

 what denser layer of protoplasm 

 in many cells, especially in many 

 unicellular animals. Opposed to 

 endoplasm, the inner, more fluid 

 mass. The ectoplasm in proto- 

 zoans corresponds to the skin of 

 higher animals. The presence of 

 a more or less sharply set-off 

 outer layer or membrane or skin 

 in all organisms whatever is 

 coming to be recognized as hav- 

 ing a more fundamental physio- 

 logical meaning than that of a 



protection for the delicate parts 

 underneath, now that so much is 



. being learned by physical chem- 

 istry about surface phenomena. 



ENERGY. Work and capacity to do 

 work. It is important to note 

 that work and capacity to work 

 necessarily imply some object, 

 organic or inorganic, to do the 

 work, and hence that when the 

 energy of a horse, or of a stream 

 of water, is spoken of the word 

 energy has a very different 

 meaning from what it has in 

 such a phrase as the "energy 

 conception" of nature or of the 

 organism, the implication in 

 these cases usually being that 

 energy is the real essence of 

 nature and of the organism, the 

 shape and other so-called static 

 attributes which all bodies pre- 

 sent, being only incidental and 

 mere appearances. 



EXZYME. A chemical substance 

 produced by an organism, plant 

 or animal, to the end of bring- 

 ing about chemical transforma- 

 tion in other substances, but 

 without itself being transformed. 

 The ptyalin of saliva by which 

 starch is changed into sugar, is 

 typical. Enzymes play a very 

 great part, especially in diges- 

 tion and nutrition, in the physio- 

 logical processes of all organ- 

 isms. 



EPIGEXESIS. That theory of devel- 

 opment of the individual organ- 

 ism which holds the organs and 

 parts to be actually new produc- 

 tions, and not merely enlarge- 

 ments or actualizations of what 

 already existed, this latter con- 

 ception of development consti- 

 tuting the theory of preforma- 

 tion. Although these opposing 

 theories were debated with fury, 

 almost, some years ago, little is 

 heard about them now though 

 none of the particular problems 

 around which the discussions 



