4 PRESIDENT S ADDRESS. 



sation is an important one on account of the large amount of 

 work that is being done upon it in bacterial laboratories through- 

 out the world, and of the benefits that are claimed to accrue to 

 mankind from the indications which are given in the practice of 

 the method. It may be briefly said that opsonins are the sub- 

 stances which exist in the blood for the purpose of so preparing 

 infectious bacteria that they can be speedily absorbed by the 

 phagocytes, and finally destroyed. A low opsonic content 

 indicates a low power of resistance, and conversely a high opsonic 

 index shows that the individual is well equipped to withstand 

 bacterial infection. It is also possible in obscure cases to diagnose 

 the kind of disease from the opsonic behaviour of the serum 

 towards various bacteria. Hitherto opsonic investigation hv^d 

 been directed towards the serum, but the Macleay Bacteriologist 

 turned his attention towards the bacterium, noting the effect of 

 conditions of growth, age, temperature, and so on. Various 

 factors which modify bacteria in their behaviour towards the 

 opsonins were elucidated. 



Dr. J. M. Petrie, Linnean Macleay Fellow of the Society in 

 Biochemistry, during 1908, carried on his investigations on the 

 rdle of Nitrogen and its compounds in plant-metabolism; and the 

 tirst instalments of the results were embodied in two papers which 

 appeared in the last Part of the Proceedings. Subsequently, in 

 preparation for a third paper on the same subject. Dr. Petrie 

 began a series of experiments with the object of attempting to 

 differentiate the proteins by fractional precipitations, and to 

 estimate the amounts of the amides, of amino-compounds, and 

 certain basic compounds present in seeds. Though a number out of 

 a rather lengthy series of experiments gave negative results, they 

 were necessary in carrying out his projected scheme of work. In 

 addition, Dr. Petrie has been successfully collaborating with Dr. 

 Chapman in carrying out an investigation of the hexone bases of 

 egg albumen. I have pleasure in announcing that the Council 

 has reappointed Dr. Petrie to a Fellowship from the 1st proximo. 

 Mr. E. J. Goddard, B.A., B.Sc, Linnean Macleay Fellow of 

 the Society in Zoology, has almost completed his first year's 



