180 PHYSIOGNOMY OF DISEASE. 



gradually, as they become accustomed to the change, they 

 give vent to their sudden and unusual sense of exhilaration 

 in what is usually described as a e mad ' careering about their 

 paddocks, their tails flying or flashing in the air. Every 

 spring, wherever there are grass parks and dairy cows, such 

 a familiar sight may be seen. Here the effect produced 

 the excitement is partly physical, partly mental. On the one 

 hand there is the sudden change to fresh or pure air, with 

 its stimulating oxygen, as well as exposure to another physi- 

 cal stimulant that of light with the opportunity for, and 

 all the invigorating effects of, muscular exercise ; while, on 

 the other, we have the sense of freedom substituted for that 

 of confinement and restraint. 



Instead of excitement we may, and often do, have the 

 opposite condition of depression as an expression of disease. 

 It is frequently marked by, or it leads to, listlessness, impa.s- 

 siveness, inertness, apathy, lethargy, or the following more 

 specific states or phenomena : 



1. Heedlessness of surroundings or events, or even of 

 the animal's own immediate interests and necessities ; equal 

 insensibility or non-sensitiveness to physical, mental, or 

 moral influences, to blows or lashes, to a master's entreaties, 

 caresses, orders, or scoldings, to the stings of flies or other 

 insect pests ; placid endurance of, or non-resistance to, 

 punishment. 



2. Self-isolation from the society of their own species, or 

 man, including self-concealment, seclusion, or hiding in 

 strange places, e.g. by the dog. 



3. Loss of appetite, abstinence from food, leading neces- 

 sarily to emaciation and general debility, and perhaps by 

 marasmus to death. 



Enough has already been said in this chapter alone to show 

 that there is the same difficulty that exists in the case of the 

 language of health, in our interpretations of the physical 

 expressions of disease. This arises from the fact that the 

 same expression may be the fruit both of healthy and of 

 diseased conditions ; and it is not always easy to determine 

 whether, in a, given case, we have to deal with health or 

 disease. 



