MODERN METHODS OF MEDICAL SCIENCE 37 



tions. Both have become comparative. Physiology undertakes the 

 study of the processes taking place in living things, anatomy their 

 form and structure. The comparative view has more slowly entered 

 into pathology, for this has been more closely in contact with clinical 

 medicine, and mostof the questions for investigation have arisen in 

 connection with the diseases of man. Disease is found in every living 

 thing, in all animal and plant life. The phenomena of disease must 

 differ according to the conditions peculiar to the organism. Strictly 

 speaking there can be little similarity between the phenomena of 

 disease in a plant and in an animal. The functions that are destroyed 

 or altered by disease are too dissimilar. But this is not true when 

 we study the closer details of disease. In both, changes are pro- 

 duced and the changes affect function. We can study unicellular 

 organisms directly under the microscope, see the changes which 

 are being produced by injurious conditions and the effects of the 

 changes. Knowledge derived from such study may be said to be 

 the basis of our conception of inflammation. The studies of plant 

 diseases have been almost entirely directed from the economic 

 side. The economic results which have come from this study by 

 enabling the prevention of disease are almost incalculable. General 

 medicine has gained by this study a greater knowledge of para- 

 sites, their mode of action and the means by which the organism 

 is protected against them. That the knowledge has been so rapidly 

 gained is due to the facilities for investigation and experimenta- 

 tion. Plant experimentation has never given offense. It should 

 be regarded on the whole as very much better that the study of 

 plant disease has been directed from the economic side, for progress 

 has been more rapid, but there would be advantage in the closer 

 association of plant and animal pathology and the extension to 

 plant diseases of questions coming from disease in man. 



Careful study of diseases in animals has been chiefly directed 

 to the infectious diseases and especially to those artificially pro- 

 duced. The questions have been chiefly those concerned with the 

 parasitic cause of disease and the mode of action of the parasites. 

 The more obscure diseases of animals have attracted but little 

 attention and only from the economic side. The phenomena of 

 disease in the higher animals have much similarity to the phenom- 

 ena of disease in man, and in certain aspects the diseases of animals 

 are more capable of investigation. Diseases are found in ani- 

 mals which are similar to the most obscure diseases in man. Our 

 ignorance of these diseases in man is due to their complexity and 

 the difficulties of investigation. To their understanding chemical 

 and physical methods are necessary, and some of these methods 

 cannot be carried out, for they may be harmful to the individual. 

 In animals we have the advantage that the disease can be inter- 



