USEFUL ALGAE — CHASE 431 



with the addition of cream and sugar as desired. There is a choco- 

 late-coated form of agar for those who do not care for it plain. 

 It is also combined with mineral-oil emulsions in a number of medical 

 preparations that are on the market. The dose prescribed for the 

 dry agar is from 2 to 4 drachms (8 to 15 grams) administered once 

 a day. 



Agar was once used as a cure for obesity. 



Glycerine suppositories have been made with agar as a vehicle, 

 but they contain only 70 percent of glycerin as compared with 90 

 percent in those made with sodium sterate. 



A preparation of agar is now used beneath bandages for healing 

 wounds. This method of healing wounds dates back to the ancient 

 Polynesians who used certain filamentous species of algae such as 

 Spirogyra to make poultices for sore eyes. A number of kinds were 

 also used by them as poultices for cuts, bruises, sores, and boils. The 

 native Hawaiians also used an infusion of Centroceros as a cathartic, 

 and Hypnea nidiflca (pi. 8 fig. 1) was employed similarly for stomach 

 troubles. 



The most important use of agar in pathology and bacteriology is 

 as a medium for the cultivation of pathogenic bacteria, of skin fungi, 

 and of yeasts. In 1881, Koch developed the use of this medium for 

 the isolation and cultivation of bacteria, and since that time agar 

 has become an essential in every hospital and research laboratory in 

 the world. Many scientists have worked on methods of preparation, 

 filtration, sterilization, adjustment of reactions, its purification, and 

 other details. Standardization of methods for its use in bacteriology 

 and biology has been effected. Agar is used in standard methods for 

 analyses of water, milk, soil, and sewage. 



In his intensive report on hypercolloidal impression materials used 

 in dentistry, Paffenbarger (1940) states that in the last few years in 

 the United States many materials containing agar have been devel- 

 oped for dental use in making impressions. He states that probably 

 the first scientist who used agar for taking impressions of living 

 tissues was the Viennese investigator, Alphons Poller, who was 

 granted a British patent on this material in 1925, and later an 

 American patent. Dr. Poller called his compound negocoll. He sold 

 the patent rights for the dental use of this material to the De Trey 

 Brothers of Zurich, Switzerland, who manufactured a modification 

 of it which they called dentocoll. Many materials of a similar nature 

 have been developed in the United States since then, and most of 

 them contain agar as the essential and important ingredient. The 

 value of agar in these materials is that the sol or liquid state is 

 reached only when the impression material is heated to practically 

 the boiling point of water. When the liquid is formed, it does not 



