Metamorphosis and the failure of language

The status of speech or speechlessness in Dr. Jekyll and Mr. Hyde is particularly interesting to me, given our conversation about the power of language to shape the rational and identity in Alice in Wonderland. I feel like one of the persistent themes of metamorphosis is the failure of voice and speech at the moment of transformation, an act that involves a loss of identity. This relationship is complicated in this story, however, as Dr. Jekyll's transformation into Mr. Hyde is presented not so much as a loss of identity as an embodiment of a separate form of identity, of a different facet of said identity. In the final chapter, Dr. Jekyll's Full Statement, Mr. Hyde is not allowed a voice - only Dr. Jekyll has the power to communicate. In spite of this, however, Dr. Jekyll describes the process of "in the beginning, the difficulty had been to throw off the body of Jekyll, it had of late, gradually but decidedly transferred itself to the other side. All things therefore seemed to point to this: that I was slowly losing hold of my original and better self, and becoming slowly incorporated into my second and worse." This strange back and forth of metamorphosis seems as though it should have some sort of implications for the status of language, and therefore authorship. Has there been some sort of failure on both sides of the divide? Can language and communication continue at all in this state of limbo? Which direction does the relationship flow? Is it the language, the ability to speak that creates the self and the "I" or the complete self and "I" that is only able to speak effectively?