4 Bulletin Wisconsin Natural History Society. [Vol. 8, No. 1. 



explained that in every pathological instance death is due to stoppage 

 of the heart-beat, arising from the effects of the sickness, which is 

 to be ranked only as a secondary cause. 



As to the question of natural — or physiological death — this form 

 of death is impossible, if Weissmann and Loeb are to be believed. 

 Such forms of death do occur, said Dr. Dernehl, though they are very 

 rare. For example among invertebrates, we have the instance of 

 natural death in the may -fly ; Metchnikoff studied this insect very 

 carefully for pathological causes, birfc was unable to discover any dis- 

 ease. Among vertebrates old age occurs more frequently in birds than 

 in mammals, the latter showing senility much more early than birds. 

 Dr. Dernehl then took up the theories of death which he said are 

 exceedingly numerous, but of which only three need be considered. 

 The first was that of Weissmann, as explained by the foregoing speaker, 

 that the individual cell does not die. The second, widely accepted 

 theory is that of Metchnikoff ; that death is due to general intoxication 

 of the animal body, arising from the toxins of the bacterise infesting 

 the intestinal canal. A third theory is Eibard's, which in many respects 

 is the same as that of Metchnikoff : namely, death begins as life sets 

 in ; fine granules of pigment appear in the cells, increasing in number 

 with age, at length becoming so numerous as to interfere with flowing 

 bodies in the cells. Since the cerebral cells are the first and most 

 strongly affected, the brain functions are accordingly first interfered 

 with, as instanced in the childishness of old age. 



Mr. Charles B. Whitnall followed, speaking on the Interdependence 

 of Animal and Vegetable in Avoiding Death. Beginning with a brief 

 definition of a living being he showed the interdependence of the 

 various cell groups of each being, saying that if one group of cells 

 would cease their functions this would interfere with the other groups, 

 thereby causing death. Mr. Whitnall then pointed out various phases 

 in the economy of nature such as the purification of the soil and 

 atmosphere, the absorption of the excreta of animals and the regulation 

 of moisture by trees; and the reciprocal scavenging of the micro- 

 organisms, that reduce the sewage to its chemical components. 



The members of the society then entered into a discussion of the 

 papers read and related subjects, as follows. Mr. Colles spoke on the 

 length of life in seeds, Mr. Whitnall on the biennial death of trees, 

 Dr. Earth called attention to the experiments on the life of eggs, star- 

 fishes, etc., now being carried on in California. Messrs. Burrill, Ward, 



