180 THE DOG m DISEASE. 



ease attacks, or, as we should more correctly say, results in 

 a greater alteration of one system or set of functions than 

 of others ; e. g., there are diseases peculiar to the digestive 

 system. However, an equally important truth is to be 

 recognized, viz., that no system can suffer alone ; the body 

 is a whole. 



It has been customary to assign a very prominent place 

 to the changes in the blood-vascular (circulatory) system 

 both in health and disease ; but it must be remembered 

 that changes in the blood-vessels are dependent in most 

 cases directly on changes in the nervous system. In all 

 diseases, as wejl as in health, the nervous system is the 

 head and director of the processes of the body. This 

 truth has for some years been rather ignored, but is again 

 being recognized. There are certain central cells in the 

 brain and spinal cord that preside over all other cells either 

 by direct government or influence or indirectly^ and their 

 action depends on the influences or stimuli that reach them 

 through the afferent or sensory nerves, while their com- 

 mands or governing influence are conveyed by the efferent 

 or outgoing nerves, the whole constituting a sort of circuit 

 which we may compare, after a fashion, to the circuit of a 

 battery. Influences of some kind, good or bad (irritation), 

 are^ always passing to and from the central cells, and any 

 doctrines of pathology or therapeutics (treatment) that 

 overlook this are radically defective. 



The preceding part of this book has dealt with dogs as 

 they are at the present day, and has explained how they 

 are to be managed to produce their best development and 

 to avoid disease. But do our best, we can not always so 

 perfectly adapt the environment to the animal that serious 



