TOUCH AND KINESTHESIS 



4'9 



of three trigeminal divisions in an orocaudal sequence. 

 The fibers of the mandit)ular division do not reach 

 as far caudally as do some fibers of the maxillary 

 division nor these as far as do some fibers of the 

 ophthalmic division. The clinical experience of some 

 observers (32, 273) led them to belie\e that the spinal 

 tract of the fifth nerve must be joined by some fibers 

 relevant for pain and temperature sensations from the 

 vagal, glossopharyngeal and intermedius nerves. 

 While this inference needs further confirmation, it 

 seems likely to be correct. The evidence in respect to 

 the ijulbothalamic tract is limited. Some data, how- 

 ever, clearly suggest that a topical organization of its 

 fibers exists here as elsewhere in the spinothalamic 

 system (55). 



A statement that the spinothalamic system is 

 topically organized, but that nevertheless considerable 

 intermingling of fibers related to different segments of 

 the skin takes place, seems a fair reflection of the 

 opinions of the majority of neurosurgeons (272). This 

 conclusion is based primarily on the common experi- 

 ence that shallow cuts into the spinothalamic tract 

 tend to produce only transient analgesias of higher 

 segmental levels of the body and that in order to 

 secure lasting and complete effects a section as deep as 

 practicable is usually necessary. If the fibers concerned 

 with pain for all parts of the body were indeed known 

 to lie quite superficially, such observations would 

 constitute a proof for the existence of extensive over- 

 lap. In fact, however, the topographical position of 

 such fibers is quite obscure. If they should lie deep, 

 and if the transient symptomatology with shallow- 

 cuts results basically from contusion or compression 

 and not transection of the relevant fibers, the actual 

 o\erlap could be quite small. The important point is 

 that the data in respect to the spinal trigeminal tract 

 suggest that its topical organization is quite precise. 

 If the clinical evidence regarding extensive overlap 

 is not considered binding there is hardly any reason 

 to suppose that the entire spinothalamic system is 

 necessarily less precisely organized than is the system 

 of the medial lemniscus. 



Ipsilateral Pathways of Spinothalamic System 



For many decades it has been a belief, and this view 

 is still held frequently, that all the fibers of the spino- 

 thalamic tract originating in the cells of the posterior 

 horn cross to the opposite side and ascend within the 

 anterolateral column. With the introduction of cordot- 

 omy operations the view was advanced that in addi- 

 tion to a contralateral tract an ipsilateral component 



of the spinothalamic system exists. Foerster & Gagel 

 (71) and Foerster (70) advocated this view and gave 

 several arguments for their belief The most cogent 

 were two observations: first, retrograde changes in 

 some cells of the posterior horn occur on the side of 

 the cord lesion (in addition to widespread changes on 

 the contralateral .side); and second, .some deficits of 

 tactile (and pain) sensations are demonstrable on the 

 side of the operation. 



Anatomically there are .some reasons to believe that 

 an uncrossed spinothalamic tract exists, for some 

 cells of the posterior horn emitting a.xons into the 

 anterolateral column of the same side have iieen 

 described (27, 156, 201) and the occurrence of ipsi- 

 lateral retrograde changes after appropriate cord 

 lesions has been confirmed (147, 178). The observa- 

 tion that electrical stimulation of anterolateral column 

 may evoke pain on the same side (236) and the rare 

 occurrence of pain which is relieved by an ipsilateral 

 cordotomy militate for the existence of the ipsilateral 

 tract. Since the electrophysiological evidence in the 

 cat and monkey is concordant with the findings in 

 man it can be inferred that an ipsilateral as well as a 

 contralateral spinothalamic tract presumably exists 

 in all mammals. 



SOME FURTHER OBSERV.JiTIONS ON SOMATIC 

 SENSORY SYSTEM 



Relaying of Somatic Afferent Impulses 



If the reasonable assumption is made that it is via 

 the main sensory afferent pathways that electrical 

 stimulation of the sensory nerve evokes early responses 

 in the first and second somatic cortical fields it appears 

 a simple matter to determine the location of the 

 relevant paths in the cord or brain stem by appro- 

 priately placed lesions in these structures. However 

 simple this method may be in principle it has proved 

 itself quite difficult in practice for it yielded occasion- 

 ally contradictory results in the hands of difTerenl 

 workers and often inconsistent results in the hands of 

 the same observers. 



Thus, Bohm (25) and Bohm & Petersen (26) 

 found in their experiments that selective sectioning 

 of the posterior columns abolished responses in the 

 somatic areas I and II (SI and SII). Bohm concluded 

 rather boldly that the discharges in the anterolateral 

 column are not relayed to the cortex. Gardner and 

 his colleagues (83-86), on the other hand, who de- 

 voted much work to this problem, arrived at conclu- 



