6â DE. EUTTAN ON THE 



however, oue goes a step further, and asks, whether it injures the bread as an article of 

 food, he finds the greatest diversity of opinion even among tliose justly regarded as 

 authorities on such questions. The problem is still further complicated, when its use 

 in the form of alum baking powder is considered. Here the alum, as such, is usually 

 destroyed, indeed this is essential if the powder be efficient, and other salts of aluminium 

 are formed, such as the hydrate or the phosphate. Hence the question assumes an alto- 

 gether different aspect, and we find many who would, without hesitation, pronounce 

 alum injurious to the system when introduced as alum, unable to decide against its use 

 in the form of baking powder. The testimony of medical and expert witnesses in the 

 many celebrated cases that have come before the courts is most conflicting. We find, 

 however, that most, if not all, the opinions expressed are based on theoretical grounds — 

 either on the physiological effect of alum as a therapeutic agent or on the probable changes 

 which alum would undergo when mixed with other substances and subjected to the 

 action of the digestive juices, but nowhere do I find that any systematic experiments have 

 been made to decide the question of its influence on digestion. 



In the present unsatisfactory state of the controversy, to form an intelligent opinion 

 of the wholesomeness of alum itself, or of alum baking powder when used in bread, that 

 opinion shovild be based on experiments, which are easily capable of verification. Such 

 experiments might be conducted either by feeding a large number of human beings on 

 alumed food and observing the effect, or by experiments in artificial digestion, conducted 

 in close imitation of nature and entirely comparative. The former method is manifestly 

 out of the question. The latter, however, has of late years proved of great value in 

 deciding many difficult questions in dietetics. Within the last few years, physiological 

 chemists, notably in Germany and in the United States, have done an enormous amount 

 of work in this department of chemical research. The field is a large oue and naturally 

 the literature of the subject is assuming formidable dimensions. The older methods of 

 experimenting have been improved or supplanted by new ones, and the relative digesti- 

 bility of most of the ordinary forms of food has been carefully worked out. The influ- 

 ence of condiments, of therapeutic and toxic agents, of elevated temperature, of dilution, 

 in short, the effect of most of the possible modifying agents, has been carefully studied. 



Some few and hurried experiments made by the author of this paper before giving 

 evidence in a recent prosecution were sufficient to show that this mode of experimenting 

 was capable of giving interesting and very constant results, of yielding, at any rate, a 

 basis of fact from which conclusions could be di-awn. The series of experiments then 

 made were repeated at leisure, and others added, till what at first seemed but the work 

 of a few weeks has occupied as many months. 



In the digestion of bread, as you are aware, all of the three most important digestive 

 juices of the body may take part, viz., the saliva, the gastric, and the pancreatic juices. The 

 first being only amylolytic, acts solely on the starch ; the second being only proteolytic, 

 affects the fibrin and gluten ; in tryptic digestion there is both an amylolitic and a pro- 

 teolytic action. While all three stages of digestion have been studied, the relative digest- 

 ibility of the different forms of bread have been studied chiefly with reference to salivary 

 and tryptic digestion. 



The experiments made may be arranged into three divisions, amz. : — 



A — Experiments on the digestion of breads made with different baking powders. 



