28 THE ROLE OF ALGAE AND PLANKTON IN MEDICINE 



the photosynthetic gas exchanges of the simple algae which contaminated 

 their laboratory equipment. However, not until the latter part of the nine- 

 teenth century was there any strong interest exhibited in the precise nature 

 of microalgae. These investigations were in three general directions : 



1. The chemical constituents of algae (carbohydrates, pigments, and 



— more recently — the nitrogenous and lipid components). 



2. Short-term biochemical experiments, e.g., photosynthesis. 



3. The growing of algae in culture. 



Cohen 177 first cultured algae in soil in the middle of the nineteenth 

 century, while Famintzin 178 in 1871 was the first to raise them in aqueous 

 medium. The initial extensive employment of microscopic algae was by 

 Engelmann 179 in 1883, in his work on photosynthesis. In 1890, Beijer- 

 inck, 180 a Dutch bacteriologist, described the first isolation of algae in 

 pure culture ; he obtained Chlorella vulgaris and Scenedesmus acutus free 

 from bacteria and all other organisms. In 1896 Molisch 181 published his 

 work showing the mineral requirements of simple algae to be similar to 

 those of higher plants. The study of Willstatter and Stoll 182 in 1913 

 pioneered our knowledge of algal pigments. In 1919 Warburg 183 recom- 

 mended Chlorella as a system in which photosynthesis might be very simply 

 studied; so thorough was he that in 1931 he received the Nobel prize 

 for his observations on cellular respiration, much of them made on 

 Chlorella viridans. Since then, Chlorella has become a standard organism 

 for studies on photosynthesis. It has also pointed the way for many 

 diverse uses of the byproducts of photosynthesis, as will be discussed later. 



By 1920 many algae had been isolated in pure culture. In 1926, 

 Roach, 184 investigating the effects of carbon compounds on soil algae, 

 first introduced quantitative methods in the study of algal growth. 



Another landmark was Barker's report 185 in 1935 on oxidative pro- 

 cesses in the colorless alga Prototheca. Pearsall and Loose 186 demonstrated 

 in 1937 that the metabolic changes in Chlorella growth are basically 

 similar to those occurring in the leaf of a higher plant. The history of 

 algal culture techniques was well summarized in 1946 by Pringsheim. 187 



Only during the past two decades have the diverse studies of algal 

 metabolism been unified into a cohesive entity. The first truly compre- 

 hensive reviews of algal physiology and chemistry were those of Myers 188 

 and of Blinks 34 in 1951. In 1953, Schussnig's handbook on plant bio- 

 chemistry 189 summarized many physiological data on phytoplankton, while 



