144 THE HORSE IN HEALTH AND DISEASE 



such an extent as to give visible signs of impairment is it possible 

 to recognize the symptoms of disease. 



A symptom may accordingly be defined as an external expression 

 of any change in structure or function. Symptoms are varied in 

 character. 



Pathognomonic symptoms are those peculiar to a certain dis- 

 ease, and by which the disease may be positively recognized. 

 Non-pathognomonic symptoms are those that do not indicate 

 any definite or specific disease, but may be common to a number 

 of diseases. They are, however, of great use, for their presence 

 may show the absence of certain diseases with which the disease 

 under consideration might be confounded. Subjective symptoms 

 are those appreciated by the affected individual alone, as pain, 

 impairment of vision, etc. Objective symptoms are those which 

 may be discovered by the examiner, and include faults in the con- 

 formation, the gait, etc. 



In veterinary practice it is impossible to determine -definitely 

 in all cases the exact period at which there is a departure from 

 the normal state and commencement of disease. This is due to the 

 fact that animals have not the power of speech to convey informa- 

 tion to man concerning internal troubles, and because the altera- 

 tions are so slight that they escape the examiner. 



THE DIAGNOSIS OF DISEASE 



Diagnosis is the art of determining the nature and location of 

 disease. It is the first step in the attempt to restore health, and 

 is invaluable in preventing the spread of communicable diseases. 

 Since disease is a deviation from the normal, it is absolutely neces- 

 sary to acquire a knowledge of the physiologic processes before one 

 is able to recognize pathologic changes. 



Experience in handling animals is the only way to learn how to 

 diagnose their diseases accurately. Inability to determine the 

 subjective feeling of the patient is not such a handicap as may be 

 supposed, because the objective examination is always possible. 

 We do not have notions, false modesty, vanity, or pride to deal 

 with in animals. 



Those changes which occur in the body as a result of external 

 influences must not be confused with symptoms of disease. To 

 illustrate, if a horse refuses feed it may be due to colic, excite- 

 ment, or to poor feed. Therefore, we must consider in making a 



