Modification of Tissue Oxidations in Vitro. 153 



later experiments muscle and liver were more extensively em- 

 ployed, because of their activity and their relative bulk. The 

 tissues were prepared by cutting into gram cubes, or chopping 

 finely, or crushing in a mortar. Both fresh and boiled extracts 

 made from crushed tissues were studied. 



It appears that the greater the area of tissue exposed, the more 

 rapid the reduction of oxyhemoglobin. Fresh extract is slower 

 in reducing oxyhemoglobin than the tissue itself; and boiled ex- 

 tract is without such effect. 



The modifying influence of magnesium sulphate, magnesium 

 chloride, sodium sulphate, sodium chloride, potassium chloride, 

 calcium chloride, cane sugar and quinine sulphate on the reduction 

 of the oxyhemoglobin solutions in the presence of the tissues and 

 tissue extracts was then studied. Different concentrations of the 

 substances were employed and as a rule reduction bore an indirect 

 ratio to the concentration. Also some significance is attributable 

 to the molecular character of the different salts for there are dif- 

 ferences in the action of solutions of equal molecular concentration. 

 But the physical character of the solution itself seems to be a very 

 important factor. Cane sugar, calcium chloride and quinine sul- 

 phate not only exhibit a marked restraining action on the reduc- 

 tion of oxyhemoglobin, but they appear to favor its transformation 

 into methemoglobin. 



In general, the results indicate that reduction of oxyhemo- 

 globin solutions under the conditions of these experiments is not a 

 very true picture of the activities of tissues in vivo, for the activity 

 varies directly with the time of removal of the tissue from the body. 

 An extract of a perfectly fresh tissue is much less powerful than an 

 extract of a tissue aseptically removed and preserved for a time 

 before making the extract. In other words, the reducing property 

 seems to be largely the result of post mortem changes. It seems 

 clear that more delicate methods of experimentation are necessary 

 for obtaining the desired information, and, therefore, another 

 series of experiments with methods having for their object the 

 preservation of the vitality of the tissues is now being conducted. 



