40 Causes of Disease. 



lation, obstruction to the respiratory passages or the rest of the 

 causes mentioned, the most common features of this mode of 

 death are found in the tar-Hke, uncoagulated, dark condition of 

 the blood (excessive presence of carbonic acid, deficient decarboni- 

 zation) and in the presence of haemorrhages in the hmg and 

 pleura. 



Excessive Functional Stimulation. 



All organic activity is accompanied by consumption of the 

 essentially functionating material of the organs and by the 

 formation of metabolic products. Both of these factors, especially 

 the accumulation of the latter substances in the tissues of the 

 organ, lead to a gradual reduction in efficiency, that is, to fatigue. 

 This is normally corrected (restoration or reconstitntion of the 

 part) during the intervals of rest, when the accession of arterial 

 blood replaces what has been lost and the lymph current sweeps 

 out the waste products (fatigue waste). Should the various or- 

 gans be required to continue their activity without intervals of 

 rest for a long time, or should they suddenly be overstrained, 

 or called into functional effort beyond their physiological ability, 

 their parenchimatous substance may be so affected by the height- 

 ened metabolism and so marked an accumulation take place of 

 the waste products of fatigue (carbon dioxide, phosphoric acid, 

 either free or combined as acid phosphates), that exhaustion or 

 wearing out results, with complete abolition of functional ability. 

 This condition is clearly pathological if tissue changes can de- 

 velop in the process and make the loss of function permanent 

 (fatty degeneration or cellular atrophy), or if the cessation of 

 function, momentary though it be. can cause in the vital organs 

 disturbances involving the general economy or the actual death 

 of the individual. 



Coincidence of other contributing causes (the weakened stage in 

 fevers, traumatism or thrombosis) favors the development of such 

 functional lesions from overexertion, as seen especially in the 

 heart, the general muscles and in the nervous system. 



General muscular fatigue and cardiac exhaustion mav be 

 the cause of death in overheated animals. Horses suffering from 

 thrombosis of the abdominal aorta and its branches exhibit siens 

 of functional disturbance of the muscles of the posterior limbs, 

 even under moderate effort, because of their poor arterial supply 

 and the accumulation of waste products from fatigue. The heart 



