Page:Popular Science Monthly Volume 28.djvu/114

106 next to the face area evolved that for the arm. And so on, the next step would be the development of the legs to run after the prey, and here is the leg-center; while, finally, the trunk-muscles are dragged in to help the limbs more effectually. To my mind this idea receives overwhelming support from the consideration of the fact that, the higher our centers are, the more they require education; the infant, for instance, in a few days shapes its face quite correctly to produce the food-inspiring yell, yet takes months or years to educate its upper limbs to aid it in the same laudable enterprise. Finally, what terrible probation some people pass through at the hands of dancing-masters before their trunk-muscles will bend into the bow of politeness!

Now to return to the lower end of the fissure of Rolando, to the areas for movements of the face: it was long ago pointed out by the two Daxes and Professor Broca that when this portion of the brain immediately in front of the face area was destroyed, the person lost the power of articulate speech, or was only capable of uttering injections and customary "strange oaths." In fact, this small portion of the left side of our brains (about one and a half square inch) is the only apparatus for expressing our thoughts by articulating sounds, and note particularly that it is on the left side. The corresponding piece on the right side can not talk, as it were. This remarkable state of things is reversed in left-banded people. In these the right hemisphere predominates; and so we find that, when this portion was diseased, there followed aphasia, as it is called. While, however, the right side customarily says nothing, it can be taught to do so in young people, though not in the aged.

Before leaving these motor areas, let me repeat, by way of recapitulation, that the only truly bilaterally acting areas are those for the lower facial and throat muscles. This is a most important fact, for the idea has recently been propounded that both sides of the body are represented in each motor region of each hemisphere. That is to say, each motor area has to do with the movements of both upper limbs, for example. In support of my contention that this is not in accordance with clinical facts, let me here show you photographs of the brain of a man who was unfortunate enough to suffer destruction of the fibers leading from one motor area. Here you see a puncture in the brain which has caused hæmorrhage beneath the fissure of Rolando and the motor convolutions in front and behind it.

In this transverse section of the same spot you see that the hæmorrhage has plowed up the interior of the brain. Here is the cortical gray matter, but its fibers leading down to the muscles are all destroyed. Now, in examining this patient I asked him to move his left arm or leg; he was perfectly conscious, and, understanding the question, made the effort, as we say, but no movement occurred. Now, if both sides of the body are represented in each hemisphere, it seems to me that such a case would be impossible, or at least that a little