RESPIRATION 265 



active form in the latex of the tree from which Japanese lacquer 

 is obtained, but also in many other plants. Many fungi contain 

 a ferment, tyrosinase, which oxidizes tyrosin, and in certain 

 animals tyrosinases have also been demonstrated. Another 

 well-known oxidizing ferment in fresh animal tissues is charac- 

 terized by the property of forming indophenol by oxidation in 

 an alkaline solution of paraphenylenediamin and ^-naphthol, 

 and may therefore be termed indophenyloxydase. The colour- 

 less solution becomes reddish or violet. This ferment is con- 

 tained in pancreas, salivary glands, spleen, thymus, and bone- 

 marrow, but has not been detected in muscle, lungs, brain, 

 kidneys, and other organs. Finally, we may mention a ferment 

 which favours the oxidation of aldehydes to the corresponding 

 acids, and is appropriately named aldehydase. Evidence of its 

 presence in most organs has been obtained, but it seems to be 

 absent from muscle, pancreas, bone-marrow, and mammary 

 glands. It is to be expected that other oxydases capable of 

 favouring oxidation of specific kinds of food substances or their 

 decomposition products will be discovered, but it would be rash 

 to conclude that this is the only way in which living protoplasm 

 can bring about the rapid oxidation which is so characteristic a 

 feature of its activity. 



The Influence of Respiration on the Blood-pressure. We 

 have already stated, in treating of arterial blood-pressure (p. 104), 

 that a normal tracing shows a series of waves corresponding with 

 the respiratory movements. 



The relationship between the respiratory phases and the rise 

 and fall of the blood-pressure is not by any means a simple and 

 invariable one. It depends upon a number of factors, which 

 need not be equally influential under different conditions or in 

 different animals (Lewis). Something depends upon the rate, 

 something upon the relative preponderance of costal and ab- 

 dominal respiration, and something probably upon the size of the 

 animal. For instance, an inspiratory rise of blood-pressure occurs 

 in man with pure diaphragmatic, and a fall with pure thoracic, 

 breathing (Fig. 112). In cats with fairly fast and not very deep 

 respiration the blood-pressure rises in expiration and sinks in 

 inspiration. With deep and slow respiration the opposite effect 

 may, upon the whole, be seen. In dogs, according to Einbrodt, 

 although the mean blood-pressure is falling for a short time at 

 the beginning of inspiration, it soon reaches its minimum, then 

 begins to rise, and continues rising during the rest of this period. 

 At the commencement of expiration it is still mounting, but soon 

 reaches its maximum, begins to fall, and continues falling through 

 the remainder of the expiratory phase. 



A partial explanation is afforded by a consideration of the 



