GLOSSARY. 733 



Protista. A term used to denote the large group of organisms 



which remain in the primitive state of a single cell during all 



their lifetime. 

 Protococcus. A unicellular vegetable organism, the protoplasm of 



.which contains chlorophyll. 

 Protoplasm, The substance which gives rise to the primitive vital 



phenomena, seen in unicellular organisms, and which is the 



chief agent in executing the functions of all the active tissues. 

 Protovertebrse. The primitive segments of the mesoblast in the 



site of the future vertebral column. 

 Protozoa. The division of the protista which has been assigned to 



the animal kingdom. 

 Proximal. A term used to denote a part relatively nearer to the 



centre. 

 Pseudopodia. A term applied to the projections thrown out by 



moving protoplasm, by means of which cells, such as amoebae, 



move. 

 Ptyalin. The ferment of the saliva. In a weak alkaline solution 



it converts starch into dextrine and sugar. 



Reflex action. The activity caused by a ganglion cell reflecting an 

 afferent impulse along an efferent nerve to the neighborhood of 

 original stimulation. 



Refraction. The bending which rays of light undergo when passing 

 obliquely from one medium to another of different density. 



Reticulum. A network ; a term applied to the interlacement of 

 fibres, such as is seen in reticulated connective tissue, etc. 



Rheoscopic frog- An arrangement by which the change in the 

 electric current of one muscle of a frog is made to act as a stim- 

 ulus to the nerve of another. * 



Saponification. The formation of soap ; the decomposition of oils 

 or fats by means of alkalies into salts of the fatty acid and glyce- 

 rin. 



Sarcolactic acid. The principal acid in dead muscle. It has a 

 dextro-rotatory power on polarized light, which ordinary lactic 

 acid does not possess. 



Sarcolemma. The delicate sheath surrounding the fibres of skeletal 

 muscles. 



Sclerotic. The fibrous coat of the eye-ball. 



