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SCIENCE 



[N. S. Vol. XXV. No. 639 



to provide the body with the indispensable 

 substance contained in the secretion of the 

 gland. It was just on that account that at 

 first the experimental results showing the 

 importance of this gland were disputed 

 by some observers: small accessory glands 

 were hidden in some cases which made the 

 apparently complete removal of both thy- 

 roids ineffective. The thyroid gland pos- 

 sesses, accordingly, four or five times more 

 tissue than necessary for the complete 

 maintenance of health and life of the 

 animal. 



In recent years some of the symptoms 

 following the removal of the thyroid gland, 

 especially the acute manifestations, are as- 

 cribed to the simultaneous removal of the 

 epithelial bodies known as parathjToids. 

 They are four in number. I do not know 

 of a statement dealing directly with the 

 question how much of the parathyroids has 

 to be removed in order to bring out the 

 pathological effects. However, in the dog 

 the parathyroids are imbedded in the thy- 

 roids, two in each lobe, and some of the 

 acute symptoms following the removal of 

 the thyroids in dogs are ascribed as stated 

 above, to the simultaneous removal of the 

 parathyroids. By the removal of four 

 fifths of the thyroids surely two and prob- 

 ably three of the parathyroids are also re- 

 moved. But since the removal of four 

 fifths of the dog's thyroids is not attended 

 with any evil consequences, we may also 

 conclude that a good deal of the substance 

 of the parathyroids can be dispensed with 

 without any ill effects. 



For the suprarenal glands it is now well 

 established that their removal is absolutely 

 fatal to the animal. Death follows within 

 nine to thirty-six hours after the extirpa- 

 tion of the glands, under conditions of low 

 blood pressure, extreme muscular weakness 

 and exhaustion. But the removal has to 

 be complete; if one tenth of the glands or 



even less is left in the body, the animal 

 shows no pathological symptoms. Here 

 again, as in the thyroid, this fact caused 

 the divergence of opinion which sprang up 

 soon after Brown-Sequard made the dis- 

 covery of the importance of this ductless 

 organ. In many of the experiments bits 

 of the tissue of that organ were left behind ; 

 besides, many an animal hides somewhere 

 accessory organs of the same type. For 

 the adrenals then it is evident that the 

 body possesses indispensable tissue at least 

 ten times as much as is necessary for the 

 maintenance of normal life. 



The brain is built on a bilateral plan. 

 In former years, when following the lead 

 of Flourens and as a reaction to the teach- 

 ings of Goll, the brain was considered as a 

 uniform organ, attending only to one func- 

 tion, some facts seemed to demonstrate 

 indeed that there is a great excess of tissue 

 in that organ, since the older experiments 

 of Flourens and newer experiments of 

 Goltz indicated that large parts of the 

 brain could be removed without serious 

 injury to life. To-day we know that the 

 brain presents a collection of many organs, 

 of many centers, the injury of each of 

 which is followed by sensory or motor dis- 

 turbances in definite areas of the body. 

 As a whole, the bilateralness of the hemi- 

 spheres does not mean the same as bilat- 

 eralness in other organs, namely a duplica- 

 tion of tissue for one and the same func- 

 tion. One hemisphere attends to the needs 

 of one side; for instance, the motor areas 

 of the right arm or right leg are located in 

 the cortex of the left hemisphere, and those 

 of the left arm and left leg are located in 

 the right hemisphere. The same is true of 

 the subcortical centers and apparently also 

 of the medulla oblongata. 



To this rule there is, however, an excep- 

 tion for the motor organs having in charge 

 such muscles or group of muscles which 



