Moreover, those born blind and deaf, or those born blind and becoming deaf very early, or those born deaf and becoming blind very early, though they may possess ever so good intelligence, and perhaps even learn to write letters, as did the famous Laura Bridgman, will invariably understand only a small part of the vocabulary of their language, and will not articulate correctly. Those born deaf are precisely the ones that show plainly how necessary hearing is for the acquirement of perfectly articulate speech. One who is deaf from birth does not even learn to speak half a dozen sounds correctly without assistance, and the loss of speech that regularly follows deafness coming on in children who have already learned to speak, shows how inseparably the learning and the development of perfect articulation are bound up with the hearing. Even the deafness that comes on in maturer years injures essentially the agreeable tone, often also the intelligibility, of the utterance. 2. The Organic Conditions of Learning to Speak. How is it, now, with the normal child, who is learning to speak? How is it as to the existence and practicability of the nervous conduction, and the genesis of the centers? In order to decide these questions, a further extension of the diagram is necessary (Fig. 3). [Illustration: FIG. 3.] For the last diagram deals only with the hearing and pronouncing of sounds, syllables, and single words, not with the grammatical formation and syntactical grouping of these; there must further be a center of higher rank, the _dictorium_, or center of diction (Kussmaul), brought into connection with the centers L S and W. And, on the one hand, the word-image acquired (by hearing) must be at the disposition of the diction-center, an excitation, therefore, passing from W to D (through _m_); on the other hand, an impulse must go out from the diction-center to pronounce the word that is formed and placed so as to correspond to the sense (through _n_). The same is true for syllables and sounds, whose paths to and from are indicated by _k_ and _l_, as well as by _g_ and _i_. These paths of connection must be of twofold sort. The excitement can not pass off to the diction-center D on the same anatomical path as the return impulse from D, because not a single case is known of a nerve-fiber that in natural relations conducts both centrifugally _and_ centripetally, although this possibility of double conduction does occur under artificial circumstances. Apart, then, from pathological experience, which seems to be in favor of it, the separation of the two directions of the excitement seems to be justified anatomically also. On the contrary, it is questionable whether the impulse proceeding from D does not arrive directly at the motor speech-center, instead of passing through W, S, or L. The diagram then represents it as follows (Fig. 4). Here the paths of direct connection _i_, _l_, and _n_ from D to M represent that which was just now