373 



Waldemar Koch [Mar. 



> a;ll physiological chemists. The chemistry of the brain 

 is 'a very 'difficult field and the separation of the lipoid substances 

 is stifl hardly possible. He spent the greater part of these years in 

 devising accurate methods of quantitative analysis. These methods 

 had been so perfected that he had secured more complete and more 

 accurate quantitative analyses of nervous tissue than any hitherto 

 made. By means of these methods he was attacking the problem 

 of the differentiation of the brain during growth; the distribution 

 of various substances in different parts of the brain; variations in 

 composition during disease; and the differences between the brains 

 of different animals. He was also engaged in separating carefully 

 the various lipoids, such as kephalin and lecithin, and in examining 

 their composition. He showed the very important fact that kepha- 

 lin exists as a potassium salt, whereas lecithin has more of an 

 affinity for sodium. His method of purification of the lipoids by 

 precipitation with chloroform and hydrochloric acid was extremely 

 useful. Among his other important contributions must be men- 

 tioned his work on the behavior of lecithin and kephalin emulsions 

 towards various salts, anesthetics and drugs, work which showed 

 one way in which these substances might influence irritability. He 

 discovered, also, that the brains of persons having the very obscure 

 insanity, dementia praecox, contained less of a certain sulfur frac- 

 tion than usual, and in his further examination of the sulfur dis- 

 tribution in the brain he isolated a lipoid-sulfur compound of very 

 interesting nature. He had prepared a considerable quantity of 

 this compound and he was engaged in studying its nature at the 

 time of his death. 



Dr. Koch's interest from the first had been in the problem of 

 the action of drugs on the nervous system. He taught pharma- 

 cology almost from the time of his graduation. He fitted himself 

 for his duties as a teacher by taking the regular medical courses in 

 pathology, anatomy, embryology and many of the clinical courses, 

 as well as by studying with Schmiedeberg in Germany. He thus 

 had a very unusually broad training and was able to look at his 

 subject from all sides, the chemical, the biological, and the clinical. 

 There are very few men in pharmacology to-day, who possess his 

 extensive knowledge and his sane, scientific and broad point of view. 



