18 MANUAL OF PHYSIOLOGY. 



branch of study, under the name Histology, has now developed 

 into a very wide subject, which is inseparable from either physi- 

 ology or anatomy. In this country histology is commonly 

 taught in the medical schools with physiology, for while the time 

 of the teachers of morphology is occupied iu expounding the de- 

 tails of descriptive anatomy, the microscope is in everyday use in 

 the physiological laboratory. Moreover, an adequate knowledge 

 of microscopic methods, and of the various form-elements of the 

 different textures of the body is one of the first essentials for phy- 

 siological study. 



As the different actions of the body are performed by different 

 tissues, which in the higher animals are grouped together as dis- 

 tinct organs, a general idea of the position and construction of 

 these different parts of the body must be acquired before the 

 study of physiology can be commenced. Anatomy and general 

 morphology are the frameworks upon which physiological knowl- 

 edge is built up. Some knowledge of these subjects must there- 

 fore precede the study of physiology, in order that the student 

 may be in a position to grasp even the simplest facts connected 

 with any physiological question. 



We shall soon find that the assistance of other sciences is also 

 indispensable to physiology. Thus every action of a living texture 

 or tissue is accompanied by some chemical change, the chemical 

 process, in fact, being commonly the essential part of the phe- 

 nomenon. The student of physiology must, then, know something 

 of the science of chemistry ; indeed, the mode of action of chemi- 

 cal elements forms quite as important a groundwork for the 

 study of the activity of the living tissues as their general form 

 or minute structure. 



Further, the laws which govern the motions of inanimate bodies 

 also control the actions of living tissues, for we cannot claim to 

 understand or recognize the existence of any laws affecting living 

 organisms other than those known to be applicable to dead matter. 

 There are a great number of activities shown by living textures 

 which we cannot explain by the recognized laws of nature. We 

 therefore use, for convenience sake, the term " vital phenomena," 

 to indicate processes which are beyond our present chemical and 



