April 18, 1902.] 



SCIENCE. 



603 



fession, the speaker well remembers cast- 

 ing liis eye over the field very dubiously. 

 There were no places for such workers, 

 and, from the pecuniary side, it was a 

 barren and unsatisfactoiy prospect. Nev- 

 ertheless, the field was so inviting in other 

 ways that it appeared to be worth while to 

 run the chances. A meager livelihood in 

 the pursuit of a most attractive line of 

 work seemed preferable to a mint of money 

 earned in an irksome profession, and so 

 the die was cast. 



How changed is the present outlook ! At 

 present, and for some time to come, the 

 demand for well-trained plant pathologists 

 (in this country, at least) is likely to be 

 considerably in excess of the supply. By 

 this I do not mean that there are not 

 already enough, and more than enough, of 

 second and third-rate workers ; and I would 

 not advise any one to enter the field who 

 has not a marked talent for this line of 

 inquiry, robust health, good training, and 

 a determination to do superior work. 



Of course, the magnificent development 

 of bacteriology and animal pathology 

 Avithin the last twenty-five years has had 

 its influence upon the study of plant 

 pathology, as it has had upon all related 

 sciences, but it does not seem to have 

 exerted as great an influence or as imme- 

 diate an influence as one would have sup- 

 posed. In general, botanists were the ones 

 upon whom the investigation of plant dis- 

 eases naturally devolved, and most of them 

 for some reason were very slow to make 

 use of the exact methods of research which 

 have led to such brilliant results in the 

 study of human and animal diseases. 

 However, as time has passed, more and 

 more men have learned how to study plant 

 diseases, and a considerable body of plant 

 pathologists, although by no means all, 

 are no longer open to the charge of ndt 

 Imowing how to pursue pathological re- 

 searches. 



Inasmuch as we have always had plant 

 diseases with us, the query is sometimes 

 raised why it is that the exact study of 

 such diseases was postponed until the end 

 of the nineteenth century. The primary 

 reason, no doubt, is that exemplified over 

 and over again in the history of the world, 

 viz., that one branch of research must often 

 wait for the development of some other 

 branch. In this case, inquiry into the 

 causes of many diseases had to wait for an 

 exact method of isolation of the parasites 

 and a knowledge of how to grow them in 

 pure cultures. It now seems to us a very 

 simple matter to separate one organism 

 from another by means of poured gelatin 

 or agar plate cultures. It seems, also, a 

 very near discovery that discontinuous 

 sterilization for a short time on three suc- 

 cessive days should render a culture me- 

 dium sterile, and that the simple interven- 

 tion of a sterile cotton plug between this 

 medium and the open air should suffice to 

 strain out all the floating organisms of the 

 air and keep the medium indefinitely ster- 

 ile. That the study of the causes of cer- 

 tain diseases should have to wait many 

 years until these simple facts had been 

 demonstrated and a knowledge of them 

 diffused among men is not less true than it 

 is remarkable. The whole science of bac- 

 teriology and all the wonderful advances 

 that have been made in the etiology of 

 obseui'e diseases really date from the time 

 when we were first able, with some degree 

 of ease and exactness, to separate out one 

 kind of organism from another and grow 

 it indefinitely in pure cultures, all of which 

 has come to pass since the year 1880. Only 

 the crude beginnings of bacteriology were 

 earlier than 1880. Prior to that time we 

 had, it is true, the fractional and dilution 

 methods of isolation, but these, although 

 capable of yielding good results, are 

 troublesome and have never appealed very 

 strongly to the mass of workers. 



