1. The plaintiff testified that he was doing his work at the time of the accident in the way in which he had been directed to do it by the servant of the defendants entrusted with the duty of instructing him. This made the question of his due care one of fact to be passed upon by the jury. That the machinery was running somewhat differently for a time before the injury was not decisive. It was still for the jury to say whether the plaintiff appreciated the resulting danger and assumed the risk to which he was subjected. O’Toole v. Pruyn, 201 Mass. 126.
2. There was evidence to the effect that the plaintiff put his hand into a space of about four inches above a pan filled with coal, which in the ordinary and normal operation of the machinery should have remained the same during the period of time required by the plaintiff for oiling, but that the pan moved up so that the space was much less and the plaintiff’s hand thereby was crushed. *518This movement of the mechanism when it should have remained at rest was of itself evidence of a want of repair which might be attributed to some negligence of the person in responsible control. This branch of the case comes within the rule stated with affluent citation of authorities in Ryan v. Fall River Iron Works, 200 Mass. 188, and in Chiuccariello v. Campbell, 210 Mass. 532. The charge in this respect was too favorable to the defendants.
This is not an instance of a simple device or a particular portion of a machine which can be easily seen and fully understood by any intelligent person and about which there is no complication, and where the plaintiff points to some special thing as the cause of the injury and does not base his claim chiefly on the automatic starting. This was a complicated mechanism made up of many parts, and the plaintiff did not undertake to particularize, but although introducing some testimony as to possible causes of the starting left his case to rest mainly on the unexpected automatic action at a time when the machine should have remained at rest ■if it had obeyed the laws of its own being and had operated as it was designed to operate. Cases like Cook v. Newhall, ante, 392, are distinguishable. A part of the plaintiff’s testimony indicates the act of an engineer in letting coal drop into the pan as the cause of his injury. Of course, if this was so, the defendants would not be liable. Cunningham v. Blake & Knowles Steam Pump Works, 208 Mass. 68. But other portions of his testimony show the automatic movement of the machinery as the cause. It was for the jury to say where the truth was in this conflict or inconsistency of evidence.
3. No question was raised at the trial as to the competency of the witness proffered by the" plaintiff as an expert. It must be assumed that the trial judge found him qualified. At all events no objection can be made successfully at this stage on the ground that he had not sufficient knowledge either of the general subject or of the particular mechanism.
4. The question to the expert witness for his opinion as to the cause of the abnormal and unexpected action of the machine was competent. His answer was largely irresponsive and incompetent, but no motion was made to strike out the answer in whole or in part, and hence the exception to the question must be overruled.
5. The same witness was permitted against the defendants’ *519objection to answer that the abnormal and unexpected action of the machine might have been avoided entirely by putting on a rocking device. This was incompetent and well may have been injurious to the defendants. The defendants owed no duty to the plaintiff to change the construction of the machinery in use at the time the employment began. The defendants’ only obligation was to keep in repair the machinery they had, and they were not required to install new or additional safety devices. Gleason v. Smith, 172 Mass. 50. Wolfe v. New Bedford Cordage Co. 189 Mass. 591. Mutter v. Lawrence Manuf. Co. 195 Mass. 517. McKenna v. Gould Wire Cord Co. 197 Mass. 406, 411.
In accordance with the terms of the report the entry must be
New trial ordered.