798 Transactions of tee American Institute. 



The first step toward the solution of this problem was made two 

 centuries ago by the patient and painstaking Dutch naturalist, 

 Leeuwenhoek, in the year 1680.* 



Leeuwenhoek discovered that yeast consists of globules floating in 

 a fluid ; but he thought that they were merely the starchy particles 

 of the grain, from which the wort was made, rearranged. He dis- 

 covered the fact that yeast has a definite structure, but not the 

 meaning of the fact. A century and a half elapsed, and the investi- 

 gation of yeast was recommenced almost simultaneously by Cagniard 

 de la Tour, in France, and by Schwann and Kiitzing, in Germany. 

 The French observer was the first to publish his results ; and the 

 subject received at his hands, and at those of his colleague, the 

 botanist Turpin, full and satisfactory investigation. 



The main conclusions at which they arrived are these : The 

 globular or oval corpuscles, which float so thickly in the yeast as to 

 make it muddy, though the largest are not more than one-two- 

 thousandth of an inch in diameter, and the smallest may measure 

 less than one-seven-thousandth of an inch, are living organisms. They 

 multiply with great rapidity, by giving off minute buds, which soon 

 attain the size of their parent, and then either become detached or 

 remain united, forming the compound globules of which Leeuwenhoek 

 speaks, though the constancy of their arrangement in sixes existed 

 only in the worthy Dutchman's imagination. 



It was very soon made out that these yeast organisms, to which 

 Turpin gave the name of Torula cerevisice, were more nearly allied 

 to the lower Fungi than to anything else. Indeed Turpin, and, 

 subsequently, Berkeley and Hoffmann, believed that they had traced 

 the development of the Torula into the well-known and very 

 common mould — the Penicillium glaucum. Other observers have 

 not succeeded in verifying these statements ; and my own observations 

 lead me to believe that, while the connection between Torula and 

 the moulds is a very close one, it is of a different nature from that 

 which has been supposed. I have never been able to trace the 

 development of Torula into, a true mould, but it is quite easy to prove 

 that species of true mould, such as Penicillium, when sown in 

 an appropriate nidus, such as a solution of tartrate of ammonia 

 and yeast-ash, in water, with or without sugar, give rise to Torulce 

 similar in all respects to T. cerevisice, except that they are, on the 

 average, smaller. Moreover, Bail has observed the development of 



* Leeuwenhoek, Arcana Naturae Detecta. Ed. Nov., 1721. 



