132 



PROCEfiDINGS OF THE ACADEMY OF 



[]\Iarch, 



Spiroptera Table XL 

 Deaths from Spiroptera among Psittaci. 



Year ending. Verminous. 



Not 

 verminous. 



Total Per cent. ! Total number 

 from all dying with of Psittaci in 

 causes. I worms, i collection. 



Mar. 1, 1906 3 



Mar. 1, 1907 16 



Mar. 1, 1908 17 



Mar. 1, 1909 20 



Mar. 1, 1910 10 



Mar. 1, 1911 12 



Mar. 1, 1912 24 



Jan. 1, 1913 11 



Total 113 



Not obtainable 



132 

 139 

 137 



268 



381 



30 



408 



As will be noted, an average of 30 per cent, of all parrots coming 

 to autopsy harbored these worms. Is it the parasite which has 

 caused death, or is this simply an example of commensalism which 

 is so common in the lower animals? 



We find (consulting our Table XI) that the percentage of birds 

 dying with worms is fairly constant, except for the year ending 

 1909, and excluding 1906 when the cases were beginning to be 

 recognized. This wouM indicate at first sight that the verminous 

 cases were only incidents, that 30 per cent, of our birds had harmless 

 worms which appeared at autopsy when the bird died from inter- 

 current disease. 



To throw further light on the subject a curve was prepared 

 showing deaths of Psittaci by months. Again there is a rough 

 parallellism between the curves of verminous and non-verminous 

 birds. The charts then would exculpate the parasite. 



Now let us consider the opposed evidence. It will be brought out 

 later that we have examined every parrot in the parrot-house and 

 found 14 per cent, of our living parrots verminous. What does 

 this mean? Correlating"^this finding with our statistics, we have 

 established two facts: 



(1) 14 per cent, of our living parrots are verminous. 



(2) 30 per cent, of all parrots dying in a year are found verminous. 

 See Spiroptera, Table XI. 



A greater percentage (in fact, proportionally twice as many) 

 of our verminous birds die as do non-verminous. To consider a 

 specific instance, suppose our bird-house contain 140 live parrots — 



