THE YEASTS CHAPMAN 299 



death in 1873, is of special interest in connection with the view 

 which is now universally held as the result of comparatively recent 

 observations. 



I will now turn to a discussion of the nature of the investigations 

 Avhich have led up to our knowledge of the character and life history 

 of the exciting cause of fermentation — that is to say, of the yeast 

 organism — and for this purpose it will be necessary for me to take 

 you back nearly 200 years from Liebig's day. Although the phe- 

 nomena of fermentation had been a matter of common observation 

 for many centuries, it is obvious that no successful attempt could 

 have been made to arrive at a knowledge of the originating cause 

 until the microscope had been sufficiently developed for the purpose. 

 The first examination of yeast itself of which we have any record 

 was made by the great Dutch microscopist, Leeuwenhoek, in 1680. 



At this stage, and before dealing with the actual results of 

 Leeuwenhoek's observations, it may be of interest to some members 

 of the society if I refer in some little detail to the instruments 

 employed by one who may justly be regarded as one of the greatest 

 microscopists of all times. Tlie following description by Martin 

 Folkes, published in the Philosophical Transactions of the Royal 

 Society in the year 1723, contains much that is historically of great 

 interest, and something tl\at may not be well known to all who are 

 present this evening. 

 Mr. Folkes says: 



It is now above fifty years since the late Mr. Leeuwenhoek first began his 

 correspondence with the Royal Society, when he was recommended by Dr 

 Regnerus de Graaf as a person already considerable by his microscopical dis- 

 coveries made with glasses contrived by himself, and excelling even those of 

 the famous Eustachio Divini, so much talk'd of in the learned world ; and as 

 he has ever since that time apply'd himself with the greatest diligence and 

 success to the same sort of observations, no doubt can be made of the excel- 

 lency of those instruments he so long use'd, so much improv'd, and upon the 

 fullest experience so often commended in his letters ; great part of which at 

 his decease he thought fit to bequeath to this society, for whom he ever ex- 

 press'd the greatest esteem and respect. He had indeed intimated this design 

 in several of his letters, and in his last will and testament gave orders that 

 Uie glasses should be deliver'd as soon as conveniently might be after his 

 decease ; which was accordingly done by the directions of his surviving 

 daughter, Mrs. Maria van Leeuwenhoek, to whose great care we are oblig'd 

 for the safe and speedy delivery of this very curious and valuable present. 



The. legacy consists of a small Indian cabinet, in the drawers of which are 

 thirteen little boxes or cases, each containing two microscopes handsomely fitted 

 up in silver, all which, not only the glasses but also the apparatus for manag- 

 ing of them, were made with his own hands ; besides which they seem to have 

 been put in order in the cabinet by himself as he design'd them to be presented 

 to the Royal Society, each miscroscope having had an object placed before it, 

 and the whole being accompany'd with a register of the same in his own hand- 



