THE BIOLOGY OF DAILY LIFE. 97 



Note how often observations are made at the tem- 

 perature of about 60 Fah. on organisms or organic 

 fluids whose normal living temperature is about 98' 6 

 Fah. (blood heat). 



What would be thought of a gardener who essayed 

 the cultivation and study of tropical orchids at a tem- 

 perature of zero ? Yet the absurdity would be much 

 less ; for orchids flourish in a wide range of tempera- 

 ture, and no great biological theory affecting the 

 welfare of humanity is rested upon their habits, not 

 even in the creative work of Darwin on Orchids. 



Now the yeast organism is literally sensitive to a 

 degree ', even of the Fahrenheit scale. It is simply 

 toipid at 60, and many degrees higher. 



The world will have cause to rejoice that Wallace's 

 early business brought him into an intimate acquaint- 

 ance with yeast and its strange habits of life. 



Later in life Wallace was engaged in another busi- 

 ness, which at first sight would seem to be entirely 

 out of the way of all physiological discovery, and yet in 

 truth was of the utmost service as a training. This was 

 the manufacture of embroidery. His eye received a 

 thorough training through the immense number of 

 specimens of work which passed under his inspection 

 as a master-manufacturer in that industry. Frequent 

 attempts to pass off previously used designs would be 

 made, and could only be guarded against by constant 

 vigilance. Thus not only the power of distinguishing 

 varieties of design, in closely resembling forms, but 

 also the facility of recognising identity and the memory 

 of forms were' cultivated to a remarkable degree. 



Every student of the history of human knowledge 

 must know that the grandest discoveries in any branch 



H 



