756 Comparative Animal Physiology 



corpora allata in female insects. Ovariectomy in Melanoplus, Calliphora, 

 and LiiciJia leads to hypertrophy of the allata, and perhaps leads to a func 

 tional alteration in still other insects, such as Sarcophaga and Leiicophaea. 



Allatectomy leads to less distinct results in male insects than in females. 

 The operation in no manner interferes with the production of sperm cells; 

 in fact, allatectomized males of Leiicophaea show ability to mate with, and 

 effectively fertilize the eggs of, normal females. There are reports, however, 

 that the male accessory glands of Rhodniiis and of Calliphora fail to show 

 normal development after allatectomy. Castration of male Leucophaea or 

 Lucilia has led to no observable modifications in the corpora allata. 



There is some evidence that the roaches, Blatta and BlatteUa, produce 

 within their ovaries a functional counterpart of the mammalian, corpus lu- 

 teum, which contributes to normal egg-producing rhythms of these species.^^ 

 In this rhythm the mature ova are laid in cocoons which are carried about 

 at the genital opening of the female. The ovaries are inhibited while these 

 cocoons are being borne, but are released to further activity after deposition 

 of the cocoons. Implantation of actively growing ovaries into the body of 

 cocoon-bearing females is followed by a rapid change of certain characteris- 

 tics of the implanted oocytes to resemble those seen in immature ovaries. 

 Extracts of ovaries from animals in the inhibited stage of the normal repro- 

 ductive cycle yield the same results. Histological examination of ovaries in 

 their normally inhibited stage showed the presence of yellowish granules 

 in the follicles formerly occupied by the developing ova. 



HORMONES AND GENERAL MAINTENANCE AND METABOLISM 



Intermediary Metabolism: Vertebrates. A number of hormones within 

 the body, arising in the anterior pituitary, thyroid, adrenals, pancreas, and 

 other organs, cooperate in their activities to help maintain the delicate bal- 

 ances obtaining in normal metabolism. The exact modes of action of these 

 hormones involved in general metabolic homeostasis are still far from com- 

 pletely known, although the general outlines of their mechanisms of action 

 have become clear. 



Much more is known about the intermediary metabolism of carbohydrates 

 than about that of the other two major categories of organic substances, the 

 proteins and lipids. In the higher vertebrate, at least, the amount of blood 

 glucose is maintained within a relatively narrow range of concentration as a 

 result of a dynamic balance between blood glucose formation in the liver 

 from glycogen stores, on the one hand, and utilization of glucose by the 

 body tissues, on the other. Muscle, despite its large reservoirs of glycogen, 

 is unable to produce glucose rapidly enough to maintain normal blood sugar 

 levels in hepatectomized individuals. These latter become profoundly hypo- 

 glycemic. Muscle, however, does contribute some glucose to blood indirectly, 

 through the escape of excess lactic acid by way of the blood to the liver, 

 where it is converted into glycogen. Glycogen is also formed in the liver 

 from the deaminized products of protein catabolism within the organism, 

 this process thus providing indirectly an additional endogenous source of 

 blood sugar. The foregoing relationships are depicted in Figure 286. 



The steps in the process of reversible glycogen formation from glucose 

 and the enzymes concerned have been considerably elucidated^*' (see also 



