iv.] YEAST. 79 



yeast, rests upon an unassailable foundation ; and the 

 inquiry into the exact nature of the substance which 

 possesses such a wonderful chemical influence becomes 

 profoundly interesting. 



The first step towards the solution of this problem 

 was made two centuries ago by the patient and pains- 

 taking Dutch naturalist, Leeuwenhoek, who in the year 

 1680 wrote thus : 



" Sgepissime examinavi fermentum cerevisiae, semperque hoc ex 

 globulis per materiam pellucidam fluitantibus, quam cerevisiam esse 

 censui, constare observavi : vidi etiam evidentissime, unumquemque 

 hujus ferment! globulum denuo ex sex distinctis globullis constare, 

 accurate eidem quantitate et formae, cui globulis sanguinis nostri, 

 respond entibus. 



" Verum tails mihi de horum origine et formatione conceptus for- 

 mabam ; globulis nempe ex quibus farina Tritici, Hordei, Avense, 

 Fagotritici., se constat aquae calore dissolvi et aquae commisceri ; hac, 

 vero aqua, quam cerevisiam vocare licet, refrigescente, multos ex 

 minimis particulis in cerevisia coadunari, et hoc pacto efficere particu- 

 lam sive globulum, quae sexta pars est globuli faacis, et iterum sex ex 

 hisce globulis conjungi." 1 



Thus 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, re-arranged. He discovered the fact 

 that yeast had a definite structure, but not the meaning 

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

 vestigation of yeast was recommenced almost simulta- 

 neously by Cagniard de la Tour in France, and by 

 Schwann and Kutzing 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 



1 Leeuwenhoek, "Arcana Naturae Detecta." Ed. Nov., 1721. 



