text: [Organization of pectoral muscle motor neurons in the rat. Contribution to the study of the axillary arch (Achselbogen)].
  In spite of their role of the forelimb activity, the organization of the mammalian pectoral muscles remains unclear. In order to get more information, we have studied, qualitatively and quantitatively, the motor pools of the various pectoral muscles in the rat (musculus pectoralis major, musculus pectoralis minor and musculus panniculus carnosus). The method applied was the retrograde transport of horseradish peroxidase by the peripheral nerves supplying the various muscles. The results provided the precise localization within the ventral horn of the motor neurons from the pectoral muscles which were all in the most ventral part of the gray matter. Three distinct motor pools were observed, which confirms the functional identity of each muscle. The motor neurons of m. panniculus carnosus exhibited some particularities. They were 4 times more numerous than those from m. pectoralis major, they occupied the whole ventral edge of the ventral horn, from its medial part to its lateral tip. The cell size was different from that of the other muscles. These results were discussed, according to the role of this muscle, which links the forelimb to the whole trunk. In mammals, m. panniculus carnosus constitutes, with musculus latissimus dorsi, the axillary arch (Achselbogen). A small area of overlapping between the motor pools of these two muscles was observed. It was suggested that the muscular fibers from the axillary arch were innervated by the same, well-defined spinal area, independent of the muscle from which they originate.
  
entities.text: ['pectoral muscle motor neurons']
entities.type: Cell
entities.entity_id: PMID-7257720_T1
entities.text: ['forelimb']
entities.type: Organism_subdivision
entities.entity_id: PMID-7257720_T2
entities.text: ['pectoral muscles']
entities.type: Organ
entities.entity_id: PMID-7257720_T3
entities.text: ['pectoral muscles']
entities.type: Organ
entities.entity_id: PMID-7257720_T4
entities.text: ['musculus pectoralis major']
entities.type: Organ
entities.entity_id: PMID-7257720_T5
entities.text: ['musculus pectoralis minor']
entities.type: Organ
entities.entity_id: PMID-7257720_T6
entities.text: ['musculus panniculus carnosus']
entities.type: Organ
entities.entity_id: PMID-7257720_T7
entities.text: ['peripheral nerves']
entities.type: Multi-tissue_structure
entities.entity_id: PMID-7257720_T8
entities.text: ['muscles']
entities.type: Organ
entities.entity_id: PMID-7257720_T9
entities.text: ['ventral horn']
entities.type: Cellular_component
entities.entity_id: PMID-7257720_T10
entities.text: ['motor neurons']
entities.type: Cell
entities.entity_id: PMID-7257720_T11
entities.text: ['pectoral muscles']
entities.type: Organ
entities.entity_id: PMID-7257720_T12
entities.text: ['gray matter']
entities.type: Multi-tissue_structure
entities.entity_id: PMID-7257720_T13
entities.text: ['muscle']
entities.type: Organ
entities.entity_id: PMID-7257720_T14
entities.text: ['motor neurons']
entities.type: Cell
entities.entity_id: PMID-7257720_T15
entities.text: ['ventral edge']
entities.type: Cellular_component
entities.entity_id: PMID-7257720_T17
entities.text: ['ventral horn']
entities.type: Cellular_component
entities.entity_id: PMID-7257720_T18
entities.text: ['cell']
entities.type: Cell
entities.entity_id: PMID-7257720_T19
entities.text: ['muscles']
entities.type: Organ
entities.entity_id: PMID-7257720_T20
entities.text: ['muscle']
entities.type: Organ
entities.entity_id: PMID-7257720_T21
entities.text: ['forelimb']
entities.type: Organism_subdivision
entities.entity_id: PMID-7257720_T22
entities.text: ['trunk']
entities.type: Organism_subdivision
entities.entity_id: PMID-7257720_T23
entities.text: ['muscles']
entities.type: Organ
entities.entity_id: PMID-7257720_T24
entities.text: ['muscular fibers']
entities.type: Cell
entities.entity_id: PMID-7257720_T25
entities.text: ['musculus latissimus dorsi']
entities.type: Organ
entities.entity_id: PMID-7257720_T26
entities.text: ['axillary arch']
entities.type: Multi-tissue_structure
entities.entity_id: PMID-7257720_T27
entities.text: ['axillary arch']
entities.type: Multi-tissue_structure
entities.entity_id: PMID-7257720_T28
entities.text: ['muscle']
entities.type: Organ
entities.entity_id: PMID-7257720_T29
entities.text: ['ventral part']
entities.type: Multi-tissue_structure
entities.entity_id: PMID-7257720_T30
entities.text: ['spinal area']
entities.type: Organism_subdivision
entities.entity_id: PMID-7257720_T32
entities.text: ['axillary arch']
entities.type: Multi-tissue_structure
entities.entity_id: PMID-7257720_T16