GLOSSARY. 



Olfactory. Pertaining to the special sense of smell. 



Omphalo-mesenteric. The vessels connecting the embryonic circu- 

 lation with the yolk sac, which are earty obliterated in the mam- 

 malian foetus. 



Ophthalmoscope. An instrument consisting of a small mirror by 

 which the interior of the eye can be illuminated so that the fun- 

 dus may be viewed. 



Optic cup. The involuted optic vesicle which is developed into the 

 retina, etc. 



Oxyhaemoglobin. The coloring matter of the red blood-corpuscles. 



Paramaecium. A unicellular organism composed of a soft mass 

 of protoplasm inclosed in a firmer case and covered with motile 

 cilia. 



Parapeptone. A stage in the formation of peptone produced in gas- 

 tric digestion. 



Pepsin. A ferment existing in the gastric juice which converts pro- 

 teids into peptones. 



Peptone. A form of albumin which is produced during the diges- 

 tion of proteids ; it is very soluble and diffuses readily through 

 membrane. 



Perilymph. The liquid surrounding the membranous labyrinth of 

 the ear. 



Peristalsis. The mode of contraction of the muscular walls of cer- 

 tain tubes, as the oesophagus and intestine, the effect of which 

 is to cause a progressive constriction, and so force the contents 

 of the tube onwards. 



Phakoscope. An instrument for estimating the changes in the shape 

 of the lens during accommodation by doubling the reflected 

 images with a prism. 



Placenta. The intra-uterine organ by means of which the fcetal 

 blood is brought into close relationship to that of the mother, 

 so as to gain nutriment and oxygen and get rid of effete matters. 



Plasma. A term meaning anything formed or moulded ; it is ap- 

 plied in physiology to indicate chemically complex kinds of 

 matter which subserve to the formation of the living tissues. 



Poikilothermic. Varying in temperature. A term applied to those 

 animals whose temperature varies with that of the surrounding 

 medium" cold-blooded animals . ' ' 



Presbyopia. A term denoting the loss of power of accommodation 

 for near vision, which accompanies old age. 



